These threads always devolve into a series of hypotheticals which have nothing to do with the facts of situation at hand.
This one is clear. It is a violation of the contract OP agreed to with AA to advertise miles for sale. He violated the agreement he chose to make. That is all there is to this one.
While it is probably true that there are any number of other frauds one could commit and not get caught, it is not always the case that they work and AA does not have to catch many people in order to make an impression.
These threads also suggest that the miles belong to the passenger. They do not. Not only does the passenger agree that they do not, but most of us would prefer that they do not. Nobody but a few gamers benefits from the tax implications of that. So, not somewhere I want to go in order to help out a few gamers.