1) almost everyone has a dynamic IP address for home Internet connection, which means it changes every time they reset their router, so if you block an IP you'd just be blocking the next people that get allocated that IP address.
2) a lot of public buildings and places like universities or work places have one public IP address and everyone in that place will show as coming from the same IP address, you block that IP address you block everyone in that building.
they haven't lasted more than a few seconds, have they? I think that's probably more efficient than requiring all new members to take off their shoes and belts and go through a whole-body scanner.
I got the last one within a minute or so :) (I like playing that game:))... I've seen a couple more today but have been beaten to it by other mods or the Ed.