A link spammer signed up on my forum and started posting links in every post he made.
I banned the guy, and submitted his username, email address and ip address to the Stop Forum Spam site - stopforumspam.com I do that with every spammer that signs up on my site.
Couple of days later the guy sends me an email saying I libeled him and he is going to sue me.
I signed up on a legal advice forum, and one of the guys there asked if I had a financial penalty clause in the rules. No I dont, but it sounds like a really good idea - so I added a rule to the user agreement.
21. Membership on this site can be revoked for any reason. 22. Financial penalty - by registering on this forum, members agree to pay $10,000 US dollars for each violation of the forum rules and or Terms of Service.