I have yet to play with an LLJK tagged member that wasn't a griefer, but that doesn't mean there aren't any that are good players. MANY times I've been tempted to launch a kick vote as soon as an LLJK member joined, but I've held back. We got deconned everytime one joined, but the player at least deserves a chance.
Banning a whole range of IP numbers is not the way to go. If some asshat decided to be a griefer and got my range of IP #s banned, I'd hunt him down like a dog... One of my coworkers plays Trem and LOVES causing problems (he likes using the names of people on the server). Yeah, I've seen him do it, and it's quite funny (when I'm not in the game that is getting pissed off). Thankfully, he is on Time Warner (adelphia here). Where was I going with this... oh yeah, bans don't work for those guys, because everytime he reboots the modem, new IP. Yeah, lame.