Take a look at this thread.. http://www.google.com/support/forum/p/Webmasters/thread?tid=4cf064ca1d0473f1&hl=en The guy with the plastic surgery site has been struggling to get his site out of this common -50 penalty that we see. He's been penalized off and on since July, crippling his business. Google employee JohnMu then comes into the thread citing that the reason he is penalized is because of link building, specifically forum signature links... FORUM SIGNATURE LINKS. Think about it, if they are cracking down and giving -50 for signature links, what are they gonna do to all your sites you have been xrumering? Probably a life ban... Be careful guys!