Doppy is right that many casino resorts do this. I think it does help, and I do appreciate it. No, it won't stop the planned, premeditated crime, but it puts a quick brake on the impulsive creep or pickpocket who might otherwise try to get in the elevator with me.
Originally Posted by Doppy
This "show your key" thing is really popular. I don't think it stops any criminals, but it does cut down on the number of drunken people wandering certain areas of hotels, especially at casino hotels, where there are a lot of drunks and idiots.