One of the worst things an event coordinator can do is allow too many photographers into their event!  If an event is to be photographed well, all photographers must be working from the same script and not stray from their assignments.  When lights are set up on a set, only the photographer working that set should be taking photographs!  Having a bunch of idiots trying to crowd in and utilize a set can cause lights to be knocked out of position, shots to be missed, or have a light stand knocked over into a guest!  Most strobe heads have a lot of high voltage energy that could ruin someone's evening (electrocutions are dangerous). 

Another reason the set should be left in the hands of only one person is that his camera is set to give high quality images using his lights without any additional flash power.  Having another flash go off when my shutter is open over exposes my shot and means retakes must be done.  Time is money and should not be wasted redoing shots that should not have been interfered with in the first place.  The weak power of point and shoot cameras are not a big problem, but the large flash units on prosumer cameras (cameras with features pros use on cameras used by people that think that the camera makes the picture) do interfere.

Then there is the problem of "jockeying for position, each of the invited idiots with cameras rushes to be at the "in" spot for taking pictures.  This is not acceptable behavior, as it means that some guests are not going to be able to enjoy themselves because an insensitive person that happens to have a camera is blocking their view.  Guests at charitable functions that are not having a good time tend to donate less!  If you feel you need more than one photographer, assign duties and an area to each of them and do not let them stray from that assignment.  When I work with other photographers, I do my best to not interfere in their shots.