Account suspended.

It's not easy to shut down any site on the internet. When it comes to forums a letter from a solicitor to who ever owns the domain can quite often do the trick (provided there is some substance to their complaint) and will get the offending content removed and potentially the site shut down. This happened with the Brighton North Stand Chat forum recently.

Next would be going after the company that hosts the domain, they'll often not want to get involved in any legal shit and will shut small sites down and tell them to move it elsewhere. Though I'm not sure this is the case nowadays as there has been some court cases which ruled that no one is responsible for comments on forums (and the like) other than the person that made them. Web hosts can't be pushed around as much as individuals, so nowadays will often tell anyone complaining to fuck off.

You've only got to look at sites like The Pirate Bay to see how difficult it is to shut a website down.