Originally Posted by
pinniped
Most of the best Marriott promotions yield either free hotel nights or bonus Marriott points. I've never done a Marriott stay where I found it advantageous to wipe out my MR# and provide an airline number.
I have thought about this a couple of times when I am points heavy and miles poor, but have not done it as of yet. Are there any repercussions that might not be obvious about doing that switch and then switch back?