DaStarBuG - 7:02 pm on Jun 24, 2011 (gmt 0)
You are forgetting that Publishers and Webmaster tend to look different on Advertisements as "normal" people.
Advertisings works with repetition. The more an advertising message is seen by a visitor the more it carves itself into the unconscious. That is why Advertisers spend millions on TV commercials. They want you to unconscious remember the transported message when buying a new product.
If you visited a store once and decided not to buy (or maybe you bought something) chances are greater that you buy from this store (again) if you see the Ad in the exact moment where you make your buying decision. And that is why re-targeting (which is different from IBA by the way but most of you are referring to) works so well.
If you feel that Ads are following you then you see re-targeted ads.
The metrics however are combined with IBA so you can't differentiate between re-targeted ads and IBA in AdSense.