JDiver

If you are purchasing from an authorised seller (aa.com, buypoints.com, etc.) it's really your decision.

If one buys from an individual or say, a seller on eBay, craigslist or a broker, that person is violating AAdvantage terms and conditions and could find their trip cancelled at the counter, only being allowed to fly if they pay a full walk-up fare, and even possible confiscation of miles, status and account closure.