"Guest With A Camera"
I've heard that some photographers can get a bit annoyed at the number of guests with cameras at weddings, to the point that an acronym has even been invented for it. Seriously? What gives the photographer the right to get upset about something like that. Any guest at the wedding has every right to take their own pictures of the day. That's what people buy cameras for.
From my point of view, the guests are my subjects, so if they're taking pictures, then I take pictures of them taking pictures.