Not a huge deal but I discovered one can still send PM's to banned accounts. I'm not certain but I'd bet thats not really the intended behavior, particularly because I think if you have email alerts setup then you'll get an email that you got a PM still. A banned account can't go change settings or anything so nothing to do from that end.
Obviously its not a big deal or anything and may even just be a simple SMF bug. Just food for thought, though not particularly tasty food.