The problem is, you can never be 100% sure. I'm sure this has happened to everyone by now. That one drama causer in the guild (I can go on for hours listing the ones we had to kick in mine) who doesn't want to stay, but doesn't want to leave. You may have thought they were cool at first, but soon enough they start showing their true colors then there's conflict, drama, and rumors going around which leads to a big mess. Then they start to get creative, join again as a "new person" then end up causing trouble again. Or another case may be, say a tower guild for example: as the leader, you don't want someone in. But that someone is your good friend's friend. Your good friend is a co leader, perm, or whatever it's called nowadays in your guild and whenever you're AFK or logged off he keeps recruiting that person, and you don't want to keep kicking them. You could take away your friend's rights or kick him, but on the other hand he/she is a good leader in this case and you don't want to do that. Perhaps it shouldn't be so much as a "guild ban" but more so of a blacklist system. It would really help a lot of guilds, including mine since I recruit based off of supports from my members. More than 90% of the time, I have no idea who the person is so I'm just taking their word on it. Beyond that, I cannot predict how that person may behave or act. But that falls back to what Simons said about not recruiting someone unless you're 100% sure you want to keep them. You don't know these things, no one does until they're plopped into the guild. Even my guild, highly selective enough as it is, runs into these problems. They probably won't be completely solved with a system like this, yes, but it does offer a good amount of help when determining recruits.