Here’s a bit of good news.
 

The California Supreme Court has ruled that bloggers and ISPs cannot be liable for posting defamatory comments written by third parties. In the ruling, the court decided that, like telephone companies, they were "common carriers", and exempt from libel laws.

As one who has worked in the ISP industry I can say it's a damn good thing too...leave policing to the police. The Internet and social politics don't mix.