Agility crested, the problem is that many times OP pays quite a bit of money for the opportunity to take photos. Depending on the show, it can be quite expensive. Not to mention you are there 12 hours a day running ragged, your travel costs, and hotel.
The problem isn't really spectators snapping shots, but people coming in and selling photos on the sly. Those people tend to slip in, hand out their cards and leave when they feel like it. Not to mention they don't have to pay the show for the privledge.
And, for dog shows, having someone snap a shot over your shoulder, with your sign is not only rude, it is stealing. The winners do not HAVE to purchase the photo, but, if they are back there behind you with their easy share camera they have probably wasted their time taking the shot. The person just used their sign ect;
I haven't run into these things, as I have not done any large shows. I do know it is a problem at large A horse shows. I do know the OP will get quite angry and WILL get management down
Tess, I still think one has to get permission from the show or pay a vendor fee to be fair. Just because the OP isn't doing those shots, doesn't mean it is a free for all.
Event photography is long hours and tough as it is. Add in people making it less lucrative and worth the while(the scabs selling at a show you are a OP) it just sucks.