Well, the crew are at fault for letting those sitting at the back dump their bags at the front. Furthermore, if the airlines actually enforced their carry on size rules, then there would be no problem getting all the carry ons onto the plane. I have noted that US travellers are shocked that European airlines actually do this. (Insert gags about Air France stewardesses and their sense of humor bypass here).
Oh, and then there is standing up when the seatbelt light is lit on a British Airways flight. You probably won't do that twice.
Last domestic flight I was on, one of the flight attendants noticed the bag dumpers, and when everyone was seated, took their bags out of the front overhead and moved them to the rear of the plane

Justice.