Not being a big fan of the "banning" thing, I'll toss this out.

Yoda, consider using Tor (link below). New tech, and not well subscribed yet, but it should in theory make it impossible to ban someone from the site since the originating IP address changes each time you connect (there are other ways to force this also, but that's a seperate discussion).

There are not a lot of Tor servers up that I can see (I'm not running on myself) but it is worth looking into if you have the time/interest/skills.