Okay, I'll be serious.
The ip address thing has been used some in the past, but in some instances it has locked out everyone who works at Microsoft or posts from UW. Some people have very stable ip addresses, due to dsl or cable connections I think, but my knowledge on the subject is pretty limited. Anyway, it's not the solution to your problem. One can keep at it, doing away with the new puppets of an individual as they can be identified, but I believe the goal is behavior modification, and only rarely is complete expulsion the desired result.