My friends account got perma-banned for basically screwing around in BG's in June 2010 when they introduced the 'report AFK' feature.
He was having internet problems and kept get disconnecting in BG's, and they deemed him to be 'duping' the system by only attacking someone every few minutes to remove the 60 seconds inactive debuff.
He got a 3 hour/24 hour / 72 hour ban in the space of 2 weeks, in some cases when he'd only play a single BG and everyone would and he'd get autobanned report him. Because at that time the report AFK system was new future, and everyone was using it on everyone who was even standing still...
He's appealed around 3 times, and he's never been given a proper reason to why he actually got perma-banned, around 90% of people in BGs just screw around nowadays or bot anyway and he actually never broke any rules.
The appeal system works perfectly fine in 99% of cases though, if you look on a certain botting forum, nearly everyone who gets banned for botting gets a 72 hour ban; then if they get perma-banned they nearly always successfully appeal it.