Coincidently, I just returned from a trip to San Francisco, during which I visited the de Young Art Museum (I know, not the Louvre). One exhibit, had a rather large painting on the wall which was protected from approach by a ring of posts and chains. I witnessed a male employee, look over each shoulder, then move the posts out of the way, allowing a nice looking female visitor to move up to and pose in front of the painting while he took her photo with her camera.
While I know little of the effects of flash on the integrity of a painting, I do agree there should be a respect shown by the visitors to a facility, related to the eminence of the place (poor choice of words perhaps, but I'm sure you get my drift). I certainly would not expect people to act the same way in the Louvre as they would at a local science fair. Personally, I believe certain art deserves quiet contemplation. Having said that, the staff who ignore (even assist) inappropriate behaviour is as much to blame as the visitor who exhibits that behaviour.