From slashdot.org:
See also: http://adsense.blogspot.com/2006/12/ad-and-image-placement-policy.html
The practice of placing images above or next to adsense banners has been around for a while â the idea is to trick visitors into thinking that the Googe Ads are clickable image captions. Unsuspecting visitors click on the ads, and the webmasters make money. Now, Google has officially announced that the practice is no longer allowed.
See also: http://adsense.blogspot.com/2006/12/ad-and-image-placement-policy.html