David Galbraith has a warning for adsense users

If your site is funded by Adsense and has a 'no commercial use' creative commons license, then any search engine or aggregator that in turn uses text ads based upon search returns or aggregated topics, is making money out of your content in exactly the same way that you do, but with less effort. [Does Google breach Creative Commons' licenses?]

In related news Google Accepts Porn Ads but Refuses Those for Guns: "A federally licensed firearms dealer in Connecticut is upset the Google search engine will accept ads for pornographic websites that illegally show their materials to underage children but will not accept ads from licensed gun dealers selling a legal product to adults."

Update via Kottke: Changed terms and conditions for Google AdSense