The only part of that that can be questioned is the "suddenly". The party I know that got axed engaged in no other behavior which could possibly be considered fraudulent by any stretch of the imagination. No buying, selling, or gifting of tickets for someone else, No hidden city ticketing. No shenanigans of any kind.

The only other unknown is the threshold -- number of cards -- at which AA decided to act. Or maybe there was none and it was strictly random. I think somebody above said it was 3, but I have no idea if that should be given any credence. The case I refer to was 8, over 2 years, for what it's worth.