I setup a change here on the board that should also help work against the spammers.
Right now the registration process requires a valid email. Once the email has been validated the user becomes registered and an automatic PM is sent to the users letting them know they need to post a message in the welcome forum. Users who fail to validate their emails after 90 days are deleted (they don't see any board content anyway).
Until users post that hello message, the only boards they see are the guest board and the welcome new members board. Once they post their introduction, within 1 hr the board will promoted them to a full registered member of the board and they will see all of our public forms.
The new change is the PM / welcome process.