I'm more inclined to agree with lem0n. I don't care what his reasoning is for logging in as someone else. Trying to access the accounts of other people who have not given permission for him to do so is not just harmless fun. It's against the most basic of rules, ones that don't NEED to be written.
That being said, I am going to write them anyway. Before USF's ban ends on Thursday (maybe Friday, depends on how these SMF forums handle it), I am going to write up some basic but very clear rules on what does and does not constitute banning, and for how long. I didn't want to have to do it at all, but I think it would be prudent now. That way there will be ambiguity. You break the rules, you suffer the clear-cut consequences. I don't want to turn this place into a Nazi death camp with everyone feeling like they're being watched and like they can't open up and have a good time, but there has to be SOMETHING basic in writing to keep this kind of nonsense from happening again.
I'll run them by you all first, though. So keep an eye on this forum the next couple days.