It depends. Casual small shows with spectators using point and shoot cameras don't matter much to me.

If I have been requested to photograph an event, usually an announcement is made in the flier and at the site that no other photography is allowed on site. Certainly the organizers and judges know I am the photographer so all the win photos are taken by me.

Sometimes someone will pull out their SLR and telephoto lenses to shoot their own family member and or pet. I don't get excited about it or too turf oriented as long as it is just a few shots.

When I am at an event and another photographer has been designated, I do not pull out my equipment except for a point and shoot to do casuals of friends and family. No one has jumped on me for that.

Have fun!