Well, just to add my 2p's worth ..I am a Moderator over on the Desktop Sidebar forums , and people who troll, flame and spam are banned immediately .. no warnings .....
Anyone who we SUSPECT of being a potential Spammer etc... will have all his/her posts previewed before
forum members get to see them ... we also run a search on the members' name .. that usually tells us
if the person needs to be watched ..
We also use Whois to do an IP trace, and report the offender/s to the IP , who should effectively deny internet access to them ...
Not foolproof , I know , but as a result of these measures we have cut all nefarious postings down to maybe just a couple per month .. which is not a bad average ...
.