Say someone joins your guild. For a while it's great to have them in there for awhile. They do something bad to upset the guild so they're kicked. Time passes on then you all think you should give them a second chance. So you do. Everything is all good and happy again then they end up doing something bad to upset the guild again. You kick them again. They keep pestering you about joining to a point where it becomes daily. So you block them and for a while that solves the problem. Later on, some "new guy" ends up joining. They're cool for a while, yet seem oddly suspicious. They end up doing something bad, or one of your members shoots you a PM one day like: "Psstt, did you know ____ is really ____?" or something like that to cause you to eventually realize it was that person on a separate account or had a name change. Wouldn't that bother you if that were the case? That's happened to me a few times; things don't get pretty when they do. I'd also prefer to have it as a form of blacklist. For people who just cannot join whatsoever. As for tower guilds this could also prove to be helpful. A hacker or lagger joins your guild to help for a while then starts misbehaving so you may guild ban them from joining so they won't give your guild a bad name. Something like this could prove to be very helpful. An IP guild ban could also be pretty useful as well. But there should be an 'unban' button, so say for example you IP guild ban someone with multiple accounts but you're friends with their brother/sister so you can unban them while all other accounts are banned.