http://en.wikipedia.org/wiki/Section_230_of_the_Communicatio...
Anyone could post libelous statements on the 50+ million blogs and forums out there, yet you've never seen "Warn HN: Monitor your blog comments for libel" -- that's because you can't be treated as the publisher or speaker, so can't be held liable for what was said.
Also not that the TOS tries to make the submitter liable for all damages _and_ cost : http://iwasntpaid.com/terms_of_submission
- Libel (laster) where allegations are not true or the defendant should have known they are not true.
- Smaad where allegations are true, or it's reasonable for the defendant to assume they are true.
In your example, you could be convicted of Smaad, unless you could show that you
1) acted in the public interest.
2) or needed to defend yourself against eg a counterclaim
3) or did not intend to harm someones good name