My camera's are in full view and the guest is advised of them before they arrive (in fact they blink with a green light that you can't miss when plugged in). The adapters are clearly marked "Camera" so the guest can unplug them when they arrive.
I have never had a complaint about the cameras (over 500 rentals) and in fact some people leave them plugged in for their own piece of mind. Some people leave them plugged in because they are plain stupid and then do stupid things in front of the camera.
The best benifit is for tracking of check-out since part of my departure instructions state to plug the cameras back in so I know you have departed. This really keeps people to the check-out time.
It is very important to make sure that you communicate they presence of the camera as in some places it's a felony to record someone without their knowledge.