The way I see it is you buy the equipment to use, so use it when you can! Since I've done enough weddings already, when I am not the official photographer I leave everything at home... Seems stupid to even think about bringing a pocket camera worried about what you may look like carrying a professional one.
My niece was married recently and group shots were somewhat of a mis-managed disaster. I could have helped, but I stayed clear since they hired a professional and I was there as a guest.