I'm Plat and on occasion stay at Marriott with one or two of my company partners. We book x number of rooms but check in individually using our own (not corporate) credit cards and Marriott cards.

I've had about five times in the last couple of months where I've checked out, only to later find that both rooms were in fact charged to my credit card despite the final bill only showing one room. Points were also just put onto one card. It's not been a major problem getting Marriott to recredit the points appropiately and a following phone call to the credit card company has resolved it quickly but it is an annoyance I could do without.

Edited to add, these have been in North American Marriotts and at different locations.

I do the same thing a every month or so but never have this problem.