Making Sense of AdSense
As I have said elsewhere, I think that Google's AdSense program is one of the biggest Win/Win/Win deals in the history of the internet. It's really pretty simple actually, you surrender control to a portion of your page real-estate and if Google can merge their content successfully with yours, you get paid. The measure of success is when the audience decides that Google has put up something that is interesting enough to be worth clicking on. So in the successful case, Google wins (because they get to charge for publishing content), web-authors win (because they get paid for providing space), and readers win (because they have more information available).
That's when it works of course. When it doesn't work you have annoying little boxes distracting from tacky design with irrelevant advertisements for Viagra. So it takes work to make everything hang together well. I personally don't resent Google's ads when I hit them on the web, although I also have to admit that I generate a lot more clicks than sales. I'm just curious about everything, and adverts do provide a very high-level overview to most subjects.
And in that respect advertising is a lovely example of informational Yin & Yang. You can't truly make a sale without teaching someone why they need a product. Advertisers must give in order to receive and that is part of why advertisements on the web are hardly as pernicious as they are on television or radio.
The biggest reason is that the Web is a very different kind of medium from broadcast media. It is not passive, it is interactive. I think people know this almost instinctively, but I am feeling particularly conscious of it right now because of of what I have been reading in Ambient Findability , by Peter Morville. In it he shows how the web is a conversation — where content is discourse, links are knowledge and clicks it's body language. We use search engines to find "outside" opinions and sometimes contrasting opinions.
Fortunately, it's not hard to return from that horrible metaphor (and it's mine, not Morville's) to the value of AdSense. And it is simply this: Information is good as long as it doesn't distract you. AdSense allows authors to provide extra information in a controlled way. And get paid for it. Does it get any better than that?