9Oct/090
RSnake: CSS History Hack Used To Ban Torrent Users
First time this hack is used in an "actual" (aka production) site. Probably one of the more creative "hacks" I've seen around: using CSS history to enumerate whether you've been visiting a particular site or not.
For more info you can find the post here, or go Google it yourself for related posts.
There is a proof of concept too for those who want to see even more.