I think if the lot is REALLY full, with almost no spaces anywhere, "stalking" people who appear to be leaving is OK, but you do have to keep in mind that you're not the only person combing the lot for an open space. So, stop as far to the right of the aisle as possible while you wait, keep your blinker on, and don't be upset if other people pass you to get by. It should not be necessary for anyone to honk at anyone.
I will go around stopped cars in parking lots, but I do it carefully, scanning for any taillights showing on the nearby parked cars. If I don't see any, I feel it's fine to very slowly pull around the waiting car.
Far worse, IMO, are people who pull up right behind stopped cars in a street parking situation where they are trying to parallel park. I live in the central city of an area with very extensive suburbs, and most of the suburban folks never have to parallel park on their home turf, so the mechanics of parallel parking are not top of mind for them. I cannot begin to count the number of times I have stopped in front of an empty parking space with my blinker on, then looked behind me to start to back in, only to find another car sitting right on my bumper. Very often I've tried putting my arm out of the window to wave them to go around, only to have them ignore it, so I have no choice but to give up and try to find another space.