This sheds new light on the stats regularly circulated about the growth of Internet advertising as a whole. Apparently, a fixed pot of money has just been getting re-allocated among various players, while Google has single-handedly been responsible for nearly all of the actual growth since 2002. Amazing.

I can see his reasoning: a way to do good is to make tons of money and give it away to help people. So if you leave potential money unearned, you’re either shortchanging yourself or the people you would have helped. This especially seems like a compelling argument when it comes to advertising, which appears to be “free” money since it is only exchanged for the momentary attention of users.

But the fact is, the absence of ads on CraigsList represents value for users. How big a value is it to not have to see a few ads? My own feeling is that it’s not all that big, but I think it’s safe to say that most people would choose a site without ads over one with ads if given the choice. And since there’s no shortage of CraigsList imitators, that translates to what could be a very important competitive advantage.

So you can view the decision to not run ads as a bet: a bet that in the long term, this will enable CraigsList to keep their lead in the market. Sure, they could run ads now and send a few billion to charity, but that would be short-lived as they lost users. GM could sell all their assets and send it all to charity too, but there wouldn’t be any GM in the morning.

Now I have no idea if Craig or anyone else at CraigsList thinks of it this way, but you can view this decision as the application of a straightforward business philosophy: listen to your users fanatically and give them exactly what they want as long as you can cover costs. By never building any excess profit cushion into your business, you never leave the door open to a competitor to undercut you. And as a bonus, customers love you.

I would even say that as everything about web apps gets easier and easier, this might well become one of the only ways to build a sustainable business on the Internet. The barriers to both building apps and to users switching are getting lower all the time. This leaves critical mass and customer loyalty as two of the only real competitive advantages left. Charging the minimum to users, both in terms of fees and distractions, is a solid strategy. It’s a way to build and defend mass and loyalty against the competitive apps that will inevitably be chasing the same users in short order.

Update:

Some commenters in the original NYT article point out that ad revenues can also be used to address the “unmet needs” of CraigsList users, and that if this investment is not made, CraigsList will lose to a competitor that does fund this additional work via ads. This is a valid point, but I’d argue that the success of CraigsList so far is evidence that the company is keeping profits at the right level to develop *only* those features that user really want. This is a judgement call, and so far at least, it looks like they’ve made the right calls.

Other commenters say that CraigsList is engaging in “predatory pricing”, and that this pricing is putting others like newspapers out of business. I don’t find this a convincing argument. Predatory pricing (or loss-leading or dumping) is when a company sells a product at a loss in order to either build market share or drive others out of the market. CraigsList is profitable. While they are not *maximizing* short-term profits, this may be exactly what is needed to stay a viable business. The fact that classified ads are not bringing newspapers the same revenues as they used to is just further evidence of this; evidence that minimizing excess profits is what’s needed to compete in a market where it’s so easy for ideas to be realized and for users to switch.

A much-touted feature of many search engine keyword auctions is that even if you bid a high amount on a given keyword, the amount you actually pay is reduced to be a penny above the next-lowest bid. This tends to make advertisers feel safer in placing bids that are high; in fact, at least in the past, it was argued that it made the best approach “truth-telling,” or bidding the actual value of what the ad is worth to you. Google even justified this by referring to Nobel prize winning research showing that such truth-telling had been proven to be the optimal strategy for bidders in “Vickrey auctions” like Google’s.

Truthful bidding is simple and easy for advertisers, and by discouraging low-bidding, tends to increase search engine revenues; so it would seem everyone wins. But as the paper shows, the system used by search engines isn’t a true Vickrey mechanism and does *not* lead to truth-telling being the optimal strategy. In fact, the paper shows that truth-telling under this system always leads to higher prices for advertisers than in a true Vickrey system.

Here’s a quick summary of the paper. If there were only one position in sponsored search listings, reducing the top bidder’s price to be essentially equal to the next highest bidder would be a “second price” auction. In reality there are multiple positions, with different values in terms of CTRs. In this case the obvious generalization, which Google and Yahoo use, is to reduce each winning bidder’s price to the next-highest bidder; this is called “generalized second price” or GSP. Vickrey-Clarke-Groves (VCG) is a more complicated system than this. VCG reduces each winning bidder’s price to be equal to the value lost to all lower winning bidders by being knocked down a position. As the paper shows, this price is always less than under GSP, and leads to truth-telling being the optimal strategy.

So a true VCG auction would better serve advertisers by really making truth-telling the best strategy and by lowering prices paid. But it would probably reduce search engine revenues as compared to the current GSP approach, and would eliminate the systems used by some sophisticated advertisers to constantly try to game GSP, which is inherently unstable and presents fleeting opportunities for gain via low-bidding. The paper points out that Ask and MSN, having less invested into GSP, have an opportunity to attain a comparative advantage over Google and Yahoo by using VCG to reduce these inefficiencies.

All this reminds me of another inefficiency in the online ad market: the high CPCs currently being paid for contextual placements due to mixing search keyword bids with contextual keyword bids. Google’s AdSense is certainly the most relevant example here. In the same way that advertisers are encouraged to bid their true value even though it might not be the most effective strategy, advertisers are also encouraged to extend their keyword bids to contextually targeted ads, even though such ads are known to have lower value than search ads. In fact, although it’s possible to enter different bids for contextually targeted ads, or to skip them altogether, the default behavior is for keyword bids to apply to all ads placed by Google anywhere; and defaults matter.

The result is that for publishers, AdSense has two enormous advantages over other ad networks:

(1) Every search advertiser on Google is by default an advertiser under AdSense. This automatically provides a large and varied pool of advertisers.

(2) The CPC paid by advertisers is by default set by the value of an audience who is actively searching for the keywords bid on. This leads to much higher prices than those actually based on the value of an audience who is just reading text containing the keywords.

In general, these advantages come at the expense of advertisers; it seems to me that this situation presents another great opportunity for competitors like Ask and MSN to differentiate themselves.

An interesting question is raised here: assuming conversion rates for contextual clicks are lower than those for search clicks, automatic inclusion in AdSense must lower the overall conversion rates for advertisers on Google. A recent report shows that indeed, Google comes in dead last among major search engines when it comes to conversion rates. The report attributes this to demographics, but maybe AdSense has just as much to do with it.

The real question, though, is this: have lower conversion rates led to lower keyword bids at Google as compared to other search engines? If so, this represents an effective transfer of money from search profits, where Google is already dominant, to buying market share in the placing of ads on other properties, where Google clearly plans to become dominant. As with the GSP/VCG issue, it’s impossible to say how much of this is accidental and how much is deliberate; but in the end, it amounts to both an impressively effective strategy for Google and a significant opportunity for competitors as these inefficiencies become understood and are wrung from the market.

Update: Ed Clarke, the Clarke in VCG, shows up in the comments! Blogs are amazing.

A (separate) emailed comment notes that Google’s “smart pricing” automatically lowers bids for contextual ad space using an algorithm that is supposed to take into account its lower value. I hadn’t been able to find any mention of this on the Google site, but searching more broadly, I found this and this: looks like this has been around since ’04. Thanks for the correction, and sorry I missed this!

The thing is, it makes me wonder even more: if “smart pricing” is really taking ROI into account accurately, why are overall conversion rates so low on Google? Maybe it really is demographics…or maybe the algorithm still results in higher than justified CPCs paid. It’s hard to know for sure, since the alorithm is not public, but two facts seem to remain: compared to other search engines, Google conversion rates are low; and compared to other contextual ad networks, Google CPCs paid are high.

As always, the picture comes before the explanation, and clicking on it will give you a bigger version. This one shows how the Google advertising system works.

—– Google —–

Since Google has been so successful in advertising, and since AdSense is currently the main player in placing ads on smaller publisher sites, it is worth going into some detail on how Google advertising solutions work. Many other companies use elements of these solutions as well, so a lot can be learned about the market in general by studying Google.

Google has two advertising programs, one for advertisers and one for publishers:

– AdWords: This program allows advertisers to buy ad inventory based on keywords. The ads may appear on Google SERPs, within Google applications, on other search engines such as AOL, and on publisher sites subscribing to the AdSense program.
– AdSense: This program allows publishers to sell ad inventory to advertisers participating in the AdWords program. Ads may be targeted either contextually or based upon search keywords entered in a site-specific Google searchbox.

So Google is both a publisher and an ad network. One reason for Google’s success as an ad network is that every advertiser customer as a publisher automatically becomes an advertiser customer as an ad network. This neatly solves the problem all “two-sided markets” have, which is how to prime one side of the market before the other exists.

—– Keyword auctions —–

Another factor in Google’s success is its pioneering use of keyword auctions in selling ad inventory. As we noted previously, a huge advantage of search is that it automatically generates very high quality targeting data, the search keywords themselves. A keyword auction increases market efficiency by linking pricing to targeting data, and also lowers Google’s cost of sales by setting prices and fulfilling purchases automatically.

The auction itself operates in a straightforward way. For each set of keywords, advertisers choose:

– The ad that will appear
– Additional targeting criteria (geo and/or specific sites)
– The maximum CPC that will be bid
– The maximum daily dollar amount of ad inventory that will be bought

For a given ad space, Google then collects all active bids on the keywords associated with the search or web page, and places ads taking into account the maximum bid amounts. To encourage advertisers to enter high bids, Google reduces the CPC of the top bidder to be just over the next highest bid.

However, a key innovation in Google’s ad placements is that the CTR for a given ad is taken into account along with the maximum bid in determining placement position. This means that an ad with a high CTR can be placed more prominently than another ad with a higher bid, but a lower CTR. This has two consequences:

– Users see more ads that other users have previously clicked on, and which are therefore presumably more relevant and helpful.
– The overall CTR of displayed ads is higher, increasing transaction volume and thus Google’s income, which is a percentage of CPC.

—– Keyword arbitrage —–

It is neither difficult nor capital-intensive to set up an intermediary site that is paid based upon leads or referrals, and then to drive users to the site by buying keyword ads. This has resulted in arbitrageurs trying to take advantage of market inefficiencies to “buy users” for less than they “sell” them.

There are several ways to approach this arbitrage, including the following:

– By acquiring better knowledge of the auction system, one can buy users that vendors have missed for a CPC that is less than vendors are willing to pay for a referral.
– By acquiring better knowledge of user behavior, one can buy users based upon non-obvious low-CPC keywords and sell them for a higher CPC or CPA to vendors.
– By adding value to the user experience, one can buy users at a CPC and sell them to vendors at a CPA that generates a profit.

It’s probably worth noting that while they do act to decrease inefficiencies in the market, the first two techniques also can tend to pollute search results with spurious links that deteriorate the user experience. However, they also increase the number of bidders in the keyword auction, thus keeping prices high and benefiting the search engine, so it’s not clear where motivations lie on this topic.

—– Tracking and reporting —–

Along with the auction mechanism itself, Google and others also provide tools for both advertisers and publishers to track and calculate various relevant quantities, including CPC, CTR, ROI, and eCPM. In order for advertisers to take advantage of these tools, they must consider two more pages in the marketing process:

– Landing page: the page that users see after clicking on an ad.
– Conversion page: the “thank you” page that users see after completing the action desired by the advertiser, such as entering information or purchasing a product.

Since the JavaScript that a publisher places on a web page in order to insert ads comes from Google, Google can do several things:

– Identify the publisher page on which the ads will appear
– Count the impression against the selected ads
– Determine technical targeting data for the user
– Place a cookie in the user’s browser

When a user clicks on an ad, the link is actually to Google, who then redirects the browser to the advertiser’s landing page. This lets Google:

– Count the click against the ad and the publisher page the ad appears on
– Identify the ad and publisher page in the user’s cookie

Finally, to track ROI advertisers must place a Google beacon on the conversion page. This lets Google read the user’s cookie and count the action for use in ROI calculations.

It’s probably worth noting that during this process, Google can collect information on ads clicked and conversions achieved per user. This comprises additional valuable targeting data on the user, and if the user is logged into a Google user account, can potentially be aggregated across browsers and computers. Google requires advertisers to make the conversion page beacon visible as a link marked “Google site stats,” which leads to a page explaining why the beacon is present and for what purposes the data will be used.

As usual, the picture comes first, with explanations to follow.

This figure shows how vendors use intermediaries as outsourced marketing in the same way that manufacturers use distributors and resellers as outsourced sales. As usual, you can click on the diagram to get a bigger version.

—– Search —–

According to our terminology, search engines are publishers: they are a web site that sells advertising space. So are sites that incorporate search in their use, such as shopping sites.

A huge advantage of search is that in performing it, a user automatically provides the highest quality user targeting data known: search keywords. Keywords tell the publisher what the user is interested in at that very moment, without causing either user inconvenience or undue privacy concerns.

In addition, search has become an important de facto interface to the Web for many users, so that ranking highly in search results and advertising on search engines has become an important factor in marketing success for many companies. The result is that search has quickly become a huge component of online ad sales, spawning an entire sub-industry in the process.

—– Search engine marketing —–

Search engine marketing (SEM) has two aspects, both of which can become complex and so are often outsourced to SEM specialist companies. The search engine results page (SERP) has two sections:

– Organic results (AKA natural results): this is the list of links that the search engine found most relevant to the search keywords according to its presumably objective search algorithm
– Sponsored links (AKA paid placements): this is the list of ads shown along with the organic results; they are usually text ads, which may either avoid distraction from or encourage confusion with organic results

Attempting to increase a web site’s rank in the organic results is called search engine optimization (SEO). SEO can range from modifying a site to be more accurately indexed by search engines to manipulating the search engine algorithm by creating false keywords, links, or other factors used to determine ranking in organic results.

The other aspect of SEM is managing paid search, that is, buying keywords on search engines and calculating the resulting ROI. Paid inclusion is a program some search engines have that allows a site to pay in order to be “guaranteed” inclusion in organic results.

—– Intermediaries —–

If you use a search engine to search for a common product, for example digital cameras, you’ll find several different types of sites in the organic and paid results:

– Manufacturer sites (e.g. Kodak)
– Distributor sites (e.g. Circuit City)
– Shopping comparison sites (e.g. PriceGrabber)
– Directories and research sites (e.g. CNET)
– Vertical specialist sites (e.g. digitalcamera-hq.com)

Distributors and value added resellers (VARs) are a normal part of the offline world of sales and fulfillment: they are vendors who buy product from the manufacturer and sell it directly to the customer. But intermediaries such as comparison, research, and specialist sites make their money in a completely different way. Instead of selling product themselves, they link the user to a vendor for purchase, and for this they are compensated.

The relationship between intermediary and vendor depends upon whether any user data is included:

– Affiliate marketing: If the intermediary simply causes the user to follow a link to the vendor site, the link is called a referral, and the intermediary is called an affiliate.
– Lead generation: If the intermediary collects and passes along data about the user such as contact information and details concerning what the user is looking to purchase, the user following a link to the vendor site is called a lead, and the intermediary is called a lead generator.

The line between affiliates and lead generators is not always distinct, but in general affiliates are smaller and more numerous, and are usually provided with a standardized way to make referrals (such as Amazon affiliate product links). Both are paid on a CPC or more often a CPA basis.

Since intermediaries are compensated by generating interest in a vendor, they can be viewed as outsourced marketing, in the same way that distributors and VARs can be viewed as outsourced sales. And just as distributors often supply VARs, affiliates can join an affiliate network, which gives them a central place to manage and track affiliate relationships with many vendors.

Next up, Part IV: Google, auctions, and arbitrage.

I’ll again put the picture first, with explanations to follow.

This depicts how ads flow from advertisers to publishers, including the roles of ad agencies and ad networks. Like last time, you can click on the diagram to get a bigger version.

In this post I’ll dive more deeply into the particular viewpoints of advertisers and publishers, and how they translate into motivations in the ad economy.

—– The advertiser viewpoint —–

From the advertiser viewpoint, the key question is:

Advertisers have traditionally viewed their activities as falling into two categories: branding and direct response. Branding builds general awareness and future likelihood to buy, while direct response attempts to directly lead to a sale. Although this line is blurring, branding is generally associated with graphical CPM ads, while direct response is associated with CPC or CPA ads.

Ads are sometimes part of campaigns that attempt to optimize effectiveness by controlling the order, duration, frequency, and context in which users see the various ads in the campaign. Campaigns can extend across various media including the Web, and managing them is often outsourced to an ad agency. This outsourcing includes coming up with actual advertisements (creative) and/or placing these ads and tracking their performance or return on investment (ROI).

ROI, which is usually expressed as the ratio of gain over investment, has traditionally been difficult to measure, since there was no way to know what ad(s) influenced a given purchase. In the case of advertising investments, ROI is sometimes called return on ad spend (ROAS), and is calculated as follows:

One of the advantages of the Web is that ROI is immediately apparent in the case of direct response ads that lead to a sale. The average profit per impression is

so the ROI is

This calculation is even more straightforward if the ad space is paid for on a CPC or CPA basis; if the action is a sale in the latter case, the ROI is simply

Thus CPC and CPA compensation shifts the risk of mis-estimating CTR and/or CR to the publisher, even though these measures are mostly affected by the creative and conversion efforts of the advertiser.

—– The publisher viewpoint —–

From the publisher viewpoint, the key question is:

The first answer is to simply maximize the quantity of ad inventory. Ad inventory depends upon page views and ad space, so publishers can either try to attract more viewers or increase the number of ads per page (which tends to adversely affect eCPM).

The second answer is to maximize eCPM. When buying ad space, advertisers are willing to pay more to reach the right users at the most receptive moment. Thus the key to increasing eCPM is user targeting and content targeting, as previously detailed. Content targeting is straightforward enough, but user targeting runs two risks:

– Asking for user data via a registration barrier is a hassle for users, and drives many of them to leave or enter false information
– Inferring user data by tracking or correlating to an offline database can raise privacy concerns

Clearly then, a key challenge for online marketing is to approach the end goal of individualized or one-to-one marketing while preserving the user’s privacy and sense of control.

Just as advertisers outsource to agencies, publishers can outsource ad sales to ad networks. Ad networks aggregate ad inventory across many publishers and provide a single place where advertisers (or agencies) can buy ad space in volume. This helps lower the cost of selling for publishers with ROS or “remnant” inventory and smaller publishers with less inventory; similarly, advertisers and agencies can more easily buy in volume, lowering their cost of buying.

Next up, Part III: Search engines and intermediaries.

I put the picture first, but the rest of this post will explain the pieces that are shown in the diagram. Note that this is a conceptual diagram, not a technical one, so for example the publisher does not transmit user segment data to the advertiser, instead segments are offered to the advertiser part of the sale of ad inventory. You can click on it to get a bigger version.

—– Ad inventory —–

A publisher has a certain amount of space on pages within the site that is set aside for ads; this is called the ad space. Then each page with ad space is served to a user some number of times during a given time period; this is called the page views.

The publisher’s ad inventory is then the ad space multiplied by the expected page views in a given time period. So a publisher’s monthly ad inventory would be the set of ads expected to be viewed by users during that month.

This seems like a pretty simple situation, but it can be complicated by various technicalities. One complication is in counting page views. For example, by page views we really mean views by a user (not for example by a robot or a search engine spider). Some concepts that are used in calculating an accurate ad inventory include:

– Hit: a request for a file on the site
– Page view: the serving of a web page, which usually includes many files, and therefore many hits
– Session: a unique destination of page views within a certain time period; usually a single IP address that has received some number of page views within 24 hours

Besides distinguishing robots from humans, counting users and ad inventory can be made more accurate by knowing if hits are actually delivered to the browser and viewed, avoiding counting spurious hits such as page refreshes, and mapping users to sessions in light of dynamic IP addresses, etc.

—– Types of ads —–

Ad inventory is characterized by various general attributes, including:

– Premium: the ad will appear on a page which is considered to be valuable beyond the number of users viewing it, e.g. the home page of a portal
– ROS (run of site): the ad will appear on any page within the site; for an ad network this is called RON (run of network)
– ROC (run of category): the ad will appear on any page within a specified category, e.g. business or music
– Targeted: the ad will appear in page views that are targeted by either content or user, e.g. an ad for golf clubs is targeted to pages that have several instances of the word “golf” or users who have expressed an interest in golf

In addition, ads come in various formats, many of which have been standardized. These include:

– Text: a short textual description and a link
– Banner: an image placed horizontally on the page
– Vertical banner: an image placed vertically on the page
– Skyscraper: a vertical banner that is taller than normal
– Interstitial: an ad that loads between two content pages
– Pop-up: an ad that creates a new browser window
– Pop-under: a pop-up that is created behind the active window
– Rich media: an ad using animation or audio/video, such as Flash

—– Ad targeting —–

Ads can be targeted in two main ways: by the content near which the ad appears (content targeting), and by the user who is viewing it (user targeting). These two techniques are part of what is sometimes called relevance marketing (as opposed to mass marketing).

Content targeting has several variants, including:

– Site targeting: targets ads to “vertical” sites that focus on a specific topic or user segment related to the ad
– Category targeting: targets ads to a category within a site (see ROC above)
– Contextual targeting: the text on a given page is analyzed and an algorithm decides which ads best match this text

Unlike content targeting, user targeting depends upon knowing something about the user’s interests. Various methods exist for obtaining user data, thereby gaining the ability to offer user targeted ad space to advertisers:

– Registration: based on data provided by the user, usually in return for premium or personalized content
– Technical targeting: based on data that can be obtained from the user’s HTTP page request, such as domain, ISP, connection speed, operating system, and browser type
– Demographic targeting: based on the user’s demographics such as zip code, age, gender, etc., usually obtained via registration or surveys
– Geo targeting: based on the user’s location, usually obtained via registration or from the IP address
– Behavioral targeting (BT): based on the user’s behavior, e.g. which kinds of pages have been viewed in the recent past
– Search keyword targeting: based on keywords the user provides in a specific search, either on a publisher site or on a search engine

In order to allow advertisers to match ads to user data, users with similar interests are often grouped into user segments or categories.

—– Compensation —–

The advertiser can pay the publisher according to several commonly used measures:

– CPM (cost per thousand): the advertiser pays a fixed amount per thousand impressions, an impression being a user seeing the ad
– CPC (cost per click): the advertiser pays a fixed amount per click, a click being a user clicking on the ad to visit the advertiser’s site
– CPA (cost per action): the advertiser pays a fixed amount per user action; the action can be an inquiry or lead (CPI, CPL), a sale (CPS), or any other kind of specified transaction (CPT)

The latter non-CPM measures are called performance-based, since the advertiser only pays based upon the ad performing, that is, generating an interaction with the user. Publishers often convert performance-based measures into an effective CPM (eCPM) by taking into account the percentage likelihood an impression will yield a click or an action; for clicks, this is called the click through rate (CTR). For example, for a CPC ad, we have:

eCPM = CPC * CTR * 1000.

For a CPA ad, the advertiser must measure the conversion rate, or the percentage likelihood a click will yield an action. If this is denoted CR, we have:

eCPM = CPA * CR * CTR * 1000.

Next up, Part II: Outsourcing ad buying and selling.

As a relative newcomer to the world of online publishing and advertising, I’ve spent a lot of time working through the details and, as I like to do, organizing my thoughts with pictures. I put together a summary which seemed to help a few people I showed it to, so I figured I’d clean it up and put it out there for everyone to check out.

I have two main purposes in doing this:

(1) I’m hoping people who have more experience than me will help out with corrections, clarifications, and comments. I’m sure I’ve missed some things and misunderstood others, and I really want to make this as accurate and useful as possible for myself and others.

(2) Once it’s been subjected to scrutiny by real experts, I’d like to put these posts into a document that can be a resource for everyone. I know that when I was looking into this stuff, I immediately ran into a lot of confusing jargon and assumptions, and no single compact introduction to help clear it up. Hopefully this can help out the next person who comes along.

OK! So I’ll start with some introductory things, and then move on the meat of it in the next post.

—– Terminology —–

To keep things consistent, I’ll use the following terminology:

– User (AKA consumer): a person surfing the web
– Browser: the user’s web browser
– Publisher: a web site that wants to sell advertising space
– Advertiser (AKA marketer): a web site that wants to buy ads
– Ad network: a company who buys advertising space from publishers and sells it to advertisers

A “publisher” refers to any web site selling ad space, and so could be an application, service, or site that might not actually “publish content” in the traditional sense. An advertiser is assumed to have a web site, since most Web ads link to a site where the user can find more information, purchase a product, etc. Finally, note that a single web site might be both a publisher and an advertiser.

—– Scope —–

There’s a bunch of terms that are used to refer to the general activity of marketing and selling on the Internet, including:

– Interactive marketing
– Online marketing
– Internet advertising

Now, there’s a lot more to the Internet than just the Web, and there’s a lot more to marketing than just advertising; but here we’ll focus on the placement of ads on web pages (which should probably be called “Web advertising,” but for some reason nobody really seems to use this phrase). Interactive marketing in general has a more general scope, some aspects of which include:

– Email marketing: ads are emailed to the user
– Adware: ads are shown by a software application downloaded by the user
– Permission marketing: the user volunteers to receive ads, by email or otherwise

Email marketing sometimes takes place without obtaining user permission and/or providing the ability to stop receiving the ads, in which case it’s called spam. Adware sometimes collects data or displays ads without user consent, knowledge and/or the ability to uninstall, in which case it’s called spyware.

OK, with that all set, the next post will cover the basics in Part I: Advertisers and publishers.