I've feck all to do with the legal proffesion but I believe (from what I have read) that for there to be a succesful libel case the allegation has to be a) untrue and b) there has to be a demonstrated loss of reputation (which has a $ value).
In the latest alleged rape case if all anyone does is name the players allegedly involved/staying at the hotel (or whatever carefully worded statement gives the game away without maikng accusation that could be proven to be untrue then a libel action is unlikely to succeed. However there are other considerations.
The press are (allegedly
) constrained by a code of conduct and since this may become a sexual criminal case where courts insist on all concerned remain anonymous then they need to be careful to avoid a) contempt of court and b) prejudicing the case to the point where it collapses as the assualt case against the Leeds players did.
As far as I'm aware no sites have been shut down, other than voluntarily to avoid any potential legal action. The law is very grey regarding the internet. If the site is hosted and owned offshore (outside the EU to be safe) then there is probably feck all any UK lawyer could do anyway. There are also grey issues about who is responsible for posts on a BB - the owner or the essentially anonymous posters who's opinion is the problem.
The other thing about libel suits is that if you have dosh for a good lawyer then they are a good way to keep people from saying what you don't want them to say (for fear of a costly law suit) as was shown by Robert Maxwell (former owner of The Mirror) who kept true allegations about his business practices and private life (allegedly) out of the press for many many years.
Essentially the small fish who are closing sites or (like the Caf) are asking for caution because the lawyers of the players allegedly involved are trawling the net to try to keep id's under wraps and site owners want to be careful even though the chances of legal action against them are slim no matter what is being said.