Not good enough. First of all, the burden would be on the web site management to monitor all content for factual statements that might be challenged, and then to determine whether they were true. Second, although false statements of fact are not generally protected by the first amendment, under Sullivan statements about public figures protected unless the writer knows or ought to know them to be false, or shows that he doesn’t care whether they’re true or false. That determination is hard to make, and the burden of making it would be on the web site management when it should be on the person who feels defamed.