Over Christmas at my mother-in-law's house, it took several tries (and one knocked over flower vase) to finally get a good picture of all of us, with nobody left out to hold the camera.  If only I'd though of this trick...

Granted, this really only works with smart phone cameras; but chances are, if you have a big fancy camera, you probably also have a big fancy tripod and don't need this trick in the first place! ;)