The problem with slander vs. non-slander is properly documenting the "truth".

I have a friend who wants to ensure that people are aware of the conduct of a medical doctor. In order to do so she collected dozens of references from reputable sources and posted them with no interpretation of the details. That doctor would have a hard time touching her.

On the other hand, saying that "blah emailed me blah" is much harder to prove (emails can be lost or forged). There is also a lot of interpretation of the facts. So the whole thing reduces to us vs. them. In other words, it could end up a legal mess.

Then again, it may not have anything to do with the law either. Such vengeance threads would just diminish the repute of our forums.