How about cameras at enter and exit of the rental place?
No we can't do that as it will end our ding and dent scam.
I travel for business and rent cars a couple of times a month. My experience with Hertz and Avis (top tier business targeted rental companies) has been that they don't do the ding and dent scam. If you return a car to one of these guys and it has all for tires, runs, and has no obvious accident dents, you won't get hassled. On the other hand, companies like Thrifty, Budget, and independents tend to give me the super picky inspection process when you check out and return the cars.
I did just rent from Hertz a couple of weeks ago and it had the new camera thing. It got the post it note treatment. Putting aside the new camera thing for a moment, I get really good service from Hertz. I arrive at the airport, walk to the stall number displayed on the big reader board (or in an email I receive about the time I land), get in the car, drive to the exit, show my ID, and I am on my way. No paperwork, sales attempts at upgrades, etc.