Should members be able to "warn" another memembers? Like on AIM, when you warn someone it's because they've done something mean to you or something. And once your warning level gets up to 100% I think you account goes slower or something.

There's a VERY big inherent problem with that: If certain users have grudges against certain other users, then the user with the grudge could feasibly abuse their warning power to fulfill their vendetta against the other user, when, it's entirely possible the user being warned did NOTHING wrong in accordance with policy.