I've set it so that new members have to be approved by me before they can post. I've deleted about a half-dozen "applications" so far this morning - there are patterns in the types of email addresses they use.
With over 900 people registered, I can't possibly go through and screen those that are already on, so if you see spam, email me through the "contact" form and I'll take care of it, and delete the poster.
Never click on a link that a spammer posts - EVER!
Jenn