You seem to have a more benign view of companies actions than me, if US Airway's view is that no one gives away $2500 for a ticket without something in return it would indeed suggest entrapment on their behalf (given they provide and promote an ability to gift). While not something I think would happen I can't really understand why they can't put some upfront validation. Seems to me a consistent theme across US airlines and hotel chains, they put up all sort of promotions without thinking them through well, and when people "take advantage" of them (but usually within T&C's) use some blanket exclusion, the "we can do what we want" clause to get out of it and close their accounts. Plenty of examples of this in recent times, US Airways is probably mild in this regards. but I still don't like it.
PS. Shayne, no I'm not really speaking out in support of your situation, I think you went too far but that then potentially endangers quite legitimate behaviour of others.