Believe it or not, that already happened. Last week I got an email reminding me of my reservation for the night of July 4th at a hotel I stayed in a couple of weeks ago. Someone at the hotel must have rebooked me by accident, or my MR number was entered into someone else's reservation by mistake. Either way, it was a reservation I did not make or need. By cancelling the reservation after reading the email, I probably saved myself a charge on my credit card. Though, if it was someone else's reservation I suppose there could have been some confusion for them at check in.