I think this may be alot more common than we think. Ive seen 2 cameras in provider's apartments and I havent been with that many. Both were large with pretty wide lens that looked more like a professional style than usual security types. The first time, it was in the kitchen on the ceiling pointed towards the room we were in. When I saw it on my way out, I was really freaked out. It seemed to not be plugged in so that calmed me a bit but when I emailed the provider afterward about it, he laughed it off saying it was nothing. Sometime later, when searching for this provider, I saw he did webcams so I figured maybe that was what the camera was for. Another time I was going for a massage in DC. After following the guy into his apartment with the table set up in the living room, I noticed a similar large, wide lensed camera pointed at the table. I said thanks but no thanks and got the hell out of there.
With regards to legality and filing charges, are you kidding me? Public outing on a hidden camera video and filing charges would be the last thing many would be worried about. Its like saying if your in a car accident that leaves you paralyzed, you can bring charges against the other driver. By then, who the hell cares.