Although strange locations and non-FIRST postings are among the activities of spambots, not all people who join CD that do those things are spammers.
http://www.chiefdelphi.com/forums/sh...d.php?t=117653
Couple weeks ago, this person not affiliated with FIRST asked a viable programming question.
From what I've seen spambots only spam when they start their own thread, not on an existing thread. My suggestion is to pre-screen new thread requests from new users.
I also like
Efoote868's suggestion about basically granting more priveliges to those with higher rep.
I recall starting a thread when I first joined and seeing a message that said my thread would be previewed by Moderators before it was posted, and that I kept checking to see if it was approved. Was this feature taken away?
EDIT: I recall once seeing a viable thread started by a new user that was edited once it was posted to be spam. So the system can be fooled.