There is a marked difference in politely taking a picture in a less crowded museum and crowding around a painting like hungry wolves raising your phone over your head trying to compete for a photo. One is barely noticeable, the other is super rude and obnoxious. The crowd alone steered me away from the Mona Lisa. I imagine now the phone/picture factor is worse than it was back then. I wish people would exercise some courtesy and judgement.