Yeah, I know it's my fault that I shouldn't have assumed that there was a 24-hour policy, but I really thought it was something that was sort of mandatory by law. I'm disappointed there isn't because this is pretty crappy - what if someone books the wrong flight? I've done that before. In this particular case, I was trying to take advantage of a pricing benefit, so I am not terribly upset with what happened.
I think it's an unethical business practice (if UA can do it, why can't AA) and while I won't swear off traveling on AA, I will consider other options before going with them.
One more gripe - when I spoke w/ AA, they suggested I e-mail customer retentions with the situation, but I was annoyed because I couldn't call them. It would have been difficult to wait for a response.