It really depends on what the agreement between the show and the OP is. Exhibitors and their friends/family will always take photos. SELLING the photos or causing a loss of sales is a different issue. friends/family shouldn't shoot over the shoulder of the OP with the win shots. I think many have gone to digital signs to mimimze this

I know at some dog shows there ARE people who are shooting candids and handing out cards. Same with horse shows.

Again, the larger shows there are written agreements. You have to have show management that will honor those. If I am at a show just taking photos of friends and for my own use, I tend to talk to the OP. Usually, they are there only to do win shots and I do not go near win shots.