Wow, this subject transfers from wedding photography, sports, horse and dog show... a couple of questions enter my mind. First, when you have a show photographer and then booth space with portrait photographers, who's payment to the club (organization) takes the top of the pole? Can the portrait photographer shoot any part of the show?
Then, when you have an artist who is collecting reference material for their artwork, where does that enter the discussion?
With almost everyone holding a camera at every event these days, copying work is taken to a new level. I have been at shows where people want to use my background to take their own pictures!
I really hate to have the public as an enemy, but protecting our work is an on going battle. And fighting other photographers makes me feel like part of the paparazzi.

I worked on a committee for PPA (Professional Photographers of America) that had us go out and test sites that might copy an image without approval. I see this issue as part of the same "big picture" on copyright. I do not think we can
control joe public. But sites like this can help us understand Joe Photographer. Glad to be part of this group.