I posted a thread about this last year!
http://amtra.com.au/v1.2/forum/viewtopic.php?t=445&sid=c187c01f105d0bf4bdc3c3c3fa91be8cRemember these are not real people signing up...just "bot" programs that se an algorithm to complete the signup process and post the spam...never to post again.
There are far far too many forums on the Internet for any group of people to spend all day creating accounts and posting spam links.
They key is to implement a measure that will interrupt the algorithm...some of which I posted in the thread linked above...as well as requiring a validation email to activate the account.
Locking forums down so private members only can post anything is one simple idea, but private forums drive up the work of moderators, and closing off forums all together to anyone except members just isnt necessary.
General access forums for a site like this is a good idea IMHO. This site has already over 2000 members and having private forums only could detract a lot of potential new, genuine members.
Implementing something simple and smart once in a while (because spam bots WILL improve their signup methods) saves plenty of headaches in the long run.
Edit: Sorry I see zemond is on the money...I still need to learn to read the whole thread before posting! :lol: