ken_b - 5:18 pm on Mar 20, 2007 (gmt 0) From the Inside AdSense blog:
Definitely sounds like an affiliate model. Especially if Adsensers are allowed to actually choose the PPA ads.
Google can help make sure you find and display the most relevant, best-performing referral ads on your site. Simply provide a few keywords to describe your site and your users' interests, and you'll see ads automatically displayed that perform best for your site. No more constant updating, rotating products, or guesswork.
From the Inside AdSense blog: