This has only happened to me once. I called MBS and they conferenced in the property's accounting department. In this case, the explanation was that because it was a period of extremely high demand (major music festival in the park immediately surrounding the hotel), and they were probably going to have to walk people, so they checked in all of the elite members' reservations that morning to ensure that elites got good rooms.

Fair enough explanation, I thought. They credited the charges with apologies, and in the end, I felt bad for screwing them by not cancelling earlier.