As many have noticed, we had problems with spambots awhile ago, but since switching to the new Q&A captcha system, it seems to have stopped 99% of them. Unfortunately, this does not stop more advanced bots, or real people, from spamming.
We try to keep on top of banning and deleting spammers, so please have a bit of patience when you see a spammer.
The only real way to stop spammers completely is to do admin approval on all new users. I've been through this on another forum, and it is a major pain if there aren't lots of people available to do the approvals. The other forum I am on only has the forum owner do approvals, and it can take weeks and repeated emails to get it approved.
If anyone has any suggestions on other things to try to stop spammers, feel free to post here, we are always looking for good ideas.