"Generally speaking, a site is not liable for user-generated content. Sites like Yelp, Facebook and Google+ would be unable to function if this were the case. Section 230 of the Communications Decency Act provides the protection and reads in part:
'No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider.'
If a site is not a publisher, then claims such ranging from defamation to slander cannot be asserted against it."
Further down, the author discusses some exceptions.