Lines and Colors says it better than I can. This bill could shut any site down that they want to. The implications are horiffying. Go and read: http://www.linesandcolors.com/
Big money has been trying to shut down the Internet for ages. If they can't make money off it, they want to destroy it. This bill just might do that.
(A lot of sites are going black in protest. I don't know how to do that to mine so consider this a symbolic shut down).