Marriott point-shorting, the bane of my Marriott Rewards membership. Happens soooo often and I think it's because the international hotels in which I exclusively stay feel more distant from corporate and that they can, and I suspect overwhelmingly do, get away with it!
Watch all your international points carefully fellow FTers. I'd say I end up point-shorted 5k-10k points every year, although the plat line always sorts it out for me...