I have an idea that might work, at least for people who just want the photos. (I understand that people photographing the show for artistic purposes might need an exception...
How about hiring an official club photographer, who will share the photos online? If necessary, charge a very small fee for access to them, then ban other cameras. Maybe too much of a pain to enforce, but I would love to have good photos of the shows I attend without the hassle of doing it myself, and without fighting for floor space with the "rock-arazzi".