... A good portion of the immaturity actually comes from some of us older users though. xD I've always been pretty bad about this, and I joined at thirteen. I'm not nearly as bad as I used to be, since now it's all just joking, but I was still definitely immature for a long time. Huge hypocrite and whatnot.
For those who are younger.. eh. Some of them may seem worse at first, but I usually notice that they get more mature over time. I'm friends now with a lot of people who used to get on my nerves like crazy. Even one girl who stole a pet from me several months ago. Esh's actually a pretty cool guy.
We shouldn't punish everyone in a group because of a few people's temporary faults. I think the only reason a site should need an age cap is because of mature site content, which we don't really have.
I guess I don't really have anything to say on the bans thing. xD Only thing I can think of is that it might be a little much on a first offence. I've seen several people come back from being banned that have learned from their mistakes and been perfectly fine on their new accounts. Losing everything and having to start over can definitely be a damper.
'Course, if a person's doing it on purpose, yes, they deserve it.