If you got caught - the first thing the hotel would have to consider is whether the room allows more than 2. Typically, two doubles/queens will allow up to 4 people. If it is a single bed room, the limit will be 2 and the hotel can point to fire and/or health codes that strictly do not allow that number to be exceeded. I would call ahead and anonymously ask them the guest max in your room. Even if it were $10/night pp more, it might be worth it for the extra room keys.