I liked this better than what Jelsoft provided, however I'm on 4.x version of vbulletin now, which is not supported.
Replacing solution with
VSA Advanced Registration (which has a similar option at least at the registration page.)
Update: it's working horribly, and I have spam all over the place because my forum allows guest posting. It looks like I'll have to turn guest posting off until NoSpam! is updated for v 4.x