Just because I live in the same street as a registered sex offender does not mean that I am one.

I am all for security and anti-spam measures but I think that dumb measures are no better than no measures at all. Blocking by IP is about as dumb as it gets. If the forum infrastructure cannot do better then so be it but please be honest and say it how it is, do not pretend that IP filtering is the bees' knees.