Many years ago at the Smithsonian Festival, a friend & I were taking the odd photo when we were bemused/offended by a guy with 3 big Nikons and long lenses around his neck. We nicknamed him "Click". He wandered up & down in front of various stages, seemingly oblivious to whose sight he blocked in the audience.
   I think I saw a stage manager explaining the propriety of it all.

In a private setting like weddings, small groups, it should be possible for organizers to control behavior. "Stop being intrusive if you want to be paid." ought to be enough.