We went back to the source of the original answer, Arnie Rothstein, to respond to this question. He writes:
Nothing is 100% secure. That's why on the back of every hotel-casino room door is a notice to take all valuables with you, lock them in your room safe (if you have one), or place them in a lock box at the cage (if offered). This notice clearly states that the hotel cannot be held liable for missing, stolen, or damaged items left in the room.
If you drive to the resort, you'll see similar signs in the parking garage advising you to remove all valuables from your vehicle, as the resort isn't liable for any theft from or damage to your vehicle while in the parking garage.
That said, room safes are as secure from burglars and thieves as anything with a lock on it. If the safe has a digital lock, you make up your own code when you occupy the room. The old key-type safes have only one key, which is stamped "Do Not Duplicate"; these keys have no room number or other identifying marks, so even if you lose it and a thief finds it, he won't have a clue which room to burglarize.
Most of these safes have an override code or key, but if you forget your code or lose your key, it's a major ordeal that requires security, a shift manager and one other employee (usually maintenance), or even an outside locksmith, to rectify. If your room safe has been broken into (without obvious signs of forced entry), suspicion would immediately focus on at most a handful of employees who have a hotel master key and the room-safe override key or code. Of course, these employees are usually the most trusted people in the place, having worked there for years and handled all kinds of sensitive tasks, plus they value their jobs much more than whatever you might have in your room safe.
Meanwhile, the room door-key codes can be disabled instantly and are changed, usually, within 24 hours of a key-employee termination. When employees are terminated, they must return all company equipment, including the master key card if they're a butler, maid, maintenance, security, etc. If they claim not to have the key, the front desk is notified and all the pass keys in the housekeeping or maintenance or security department will be disabled and all that department's employees who are required to carry a mater key key will have to be issued a new card. (In the instance of older hotels with regular keys, a whole new master-key system has to be implemented, which necessitates manually rekeying all the hotel room doors, so those master keys are treated like plutonium.)
This is proper protocol. Is it always followed to the letter? I wish. But it's no free- for-all either, as security of the master keys, override codes, and the like is tight, with easily followed paper trails and strict accountability. Thus, keeping your valuables in the room safe is the most security you'll get out of a hotel room.
