I used a room key that didn't have my name on it. I signed the back and could use it for anything. They never asked for ID. They never really inspected the signature to see that the names didn't match. In fact, they would call my by the name on the card, not the name I signed. I wouldn't leave it in the hands of CM's!
Having said that, If you want added security in case you lose your card, set a limit at the front desk. Once your limit is met, no charges are allow until the room key is swept to a CC.