This is a pretty popular topic at the moment. Guests and their cameras during the ceremony. Yes everyone wants to get the shot but bare in mind your photographer NEEDS to get the shot. I can't count on my hands how many times someone has stepped out in to the aisle to take a photo while I was crouched down to get my shot running a very important photograph.
If at all possible advice people not to bring cameras to the ceremony because it could mean you don't get the shots you want. Many people put a blanket ban on cameras and photos at their wedding advising guests to just enjoy every moment.