Chuck, you should check out this
vb.org mod that really stops the spambots from registering. I run the version for vb4 but here is the vb3 version. It works great! Has a lot of options, most I turn off, and just let it check ip, username, and email against the StopForumSpam database.
[GlowHost] Spam-O-Matic for vB 3.8 (StopForumSpam, Akismet, Auto-Moderation and more) - vBulletin.org Forum