I find it interesting, David, that you look at it as a "power" issue. I guess that's where we differ. I don't see those situations as a power transaction. If/when I point a camera at a stranger, celebrity or not, I yield to requests not to photograph just about as often as I don't. It is the polite thing to do and has little to do with who is more poewful. Maybe that is what you mean when you talk of just being two people in an elevator.
Where I live it is common to interact with celebrity folks. I find that these interactions ALWAYS are more pleasant when dealing with them just like any other human.. not as a high-and-mighty celeb. Some are so ego-filled that they make that impossible, but most are just regular folks most of the time.
I would only be shocked at my own behavior if I was overtly rude to a celeb who asked not to be phographed, but don't shock myself so much if I just continue to snap a photo despite such a request. I don't analysze these situations too much past that.