It's been a while since I flew AA but how big as the zone numbers on their boarding passes? Based on what I've seen from other airlines what has impressed me in this thread is the ability for someone to read another person's boarding pass.

If you know the person is in your zone it's rude to go in front of them. If you are in the queue to board it's best to not leave big spaces in front of you as someone might not unreasonably surmise you are in another zone and slip in ahead of you.