Some photographers get a bit irritated at the number of guests taking pictures at weddings these days. Personally, I really like it. There's no point in trying to restrict guests' photography. I quite often incorporate pictures of people taking pictures of other people in my coverage. This is a typical example of what can happen during the cake-cutting.
I did a quick picture from the front of the couple as they looked out across the sea of cameras, but then I quickly went around behind them to make the guests the focus of the picture. And then there was the kiss. I much prefer this picture to the possible picture I would have got if I'd been looking the other way.
There's more on this subject at the Wedpix site here : Other Cameras at the Wedding