I've actually been banned before. I'm afraid it's not the kind of story you're looking for though.
I picked up League of Legends while I was away from home at college. The semester ended, and I went home for Christmas. Of course, I still wanted to play League while I was on break, but my family wanted to do activities together. I would think I was free for long enough to play a game, I'd start a game, then my family would tell me we were running off to do this or that and I'd have to AFK.
On Dec 24th I got a warning that I had a "level 1 Leaver penalty".
On Dec 25th I got a one (1) day ban.
I don't think I bothered to try and play much more that break, or asked if it would be OK to play for 45 minutes before sitting down for a break.
That's it. That's my ban story. It was a much different punishment system back then.