That may have been tongue in cheek, but why? AFAIK photography is permitted in most parts of most airports. I always take a few quick snapshots of any blemishes on a car when I take it out, and of the whole car on return if an employee isn't verifying and giving me a receipt on the spot. This is at both local and airport locations. I've never thought to take a picture or video of the keys going into the slot, but it's a good idea and I will now. Presumably there isn't really anyone around to complain when you have to do that anyway.

(yes, photos and timestamps can be altered, but should still tip the preponderance of evidence unless the rental company has their own "official" set that contradict mine, which is often all we want them to provide in the first place when they claim loss/damage)