My friend Sai is trying to find interesting ways to exploit a weakness in CSS. It'll make more sense if you read the page, but basically he's training an AI to recognize returning users regardless of which computer / browser / OS they log in from. It doesn't do anything unless or until you hit the button.

http://cssfingerprint.com/

Please follow Sai's wishes, and share the link by word of mouth, but not via Fark, Slashdot, or any of the other "big name" sites.