As reported by Inside Google:
Google is testing out a new functionality for AdSense that allows users who are not satisfied with the current ads being served to choose a different set of ads. This is a just unbelievable idea. Google is truly pushing the idea that its ads are more than just ads, they're useful, and I commend it.
There's an example on this page.
Interesting stuff.
Posted by jzawodn at January 25, 2005 09:40 AM
That's very interesting. What I find odd about it, though, is that they allow you to even type in your own topic for the ads. When I first saw that there were a few category choices to click on, that made sense. But then when I noticed the prompt for a category, I just couldn't get past thinking that I was now searching for ads.
This is nothing new. I was experimenting with something very similar almost 2 years ago. Its against the Google Adsense terms of use so I haven't revealed it. My guess is these guys just found it now and are messing around. Likely nothing Google will reveal.
See http://tim.blog.kosmo.com/blog/_archives/2005/2/8/309593.html