CDA to the Rescue!
The Communications Decency Act (47 USC Section 230(c)(1)) ("CDA") exculpates service providers for content on their systems. The California Supreme Court applied the CDA in Barrett v. Rosenthal (see http://www.courtinfo.ca.gov/opinions/documents/S122953.PDF) to find that the operator of a web site was insulated from liability as a "distributor" of defamatory statements, reversing the Court of Appeals and applying Zeran v. America Online,Inc. (4th Cir. 1997) 129 F.3d 327, 331-333.
The CDA has become the poster boy for all providers of allegedly actionable content on the Internet. This is a perfect example of how broadly a court will go to make Section 230 apply out of concern for the supposedly chilling effect a contrary holding would have. But should Rosenthal really have been insulated? She knew about the allegedly defamatory posts. What if someone instead of posting to a web site had painted the statements on Rosenthal's garage door and she permitted them to remain?