I almost got walked in once (deadbolt stopped it) when I was in the room enjoying someone.

The were trying to deliver my laundry and ignored the DND sign on the door after knocking and receiving no answer. So, they figured they could just come in. Since it would be uncomfortable for everyone involved, I did not complain

I have also checked into a room (not Marriott) that had a toy water gun and used bath robe. Moved to another room, dropped off my camera equipment, came back could not open the door and all my stuff disappeared (ended up at the front desk) after security opened the door. The hotel (Tropicana in LAS) must have had room allocation problems that day. Ended up in a suite.