[OT] Liability of Moderator

[Chris]

A short OT question: A friend of mine wants to set up a forum or 
mailing list and would like to know to which extent the moderator 
or owner of the forum is liable, if some random troll or member 
puts libelous, insulting or racist remarks on the forum. I guess 
it depends mainly on national laws, but is there some general 
"I'm not responsible for anything"-clause in the terms & 
conditions that subscribers have to accept. If not, it would be 
very dangerous to set up a forum or mailing list. Thanks for any 
hints, links or tricks.