Schutzee:

That limit is only the case for straight mileage transfers. But that's not what I'm talking about now. Marriott actually transfers miles to UA and possibly AA when you order flight or vacation package awards that include air travel. So that make the transfer limits completely irrelevant for these airlines because the flight and vacation awards yield more miles than the straight mileage transfers do. My parents have used the 200k vacation package award code #713 and asked for Hawaii as the destination. They received 70k miles in their UA account, a cert good for 7 nights at ANY Marriott (1 year expiration), a 100 minute phone card, and a Hertz discount cert. I believe that if they had asked for Australia, they would have received 120k UA miles, or India 160k miles. These awards are not actually the mileage awards that are subject to the two per year limitation. The only limit or cap that would seem to be a problem here would be a limit on LP transfers to Marriott, not on use for flight or package awards once the miles become Marriott points. The details of the package vacation awards are at:
http://www.marriottrewards.com/awards/tpackage.asp

The rules for these awards even state that you can use the various components (air, hotel, etc.) separately. As mentioned on the Marriott forum, Marriott apparently has no way of knowing how you use the UA miles after they send them to United. I'm not sure if they even care.