photobombing is but I was not sure if there was a word for another practice with photography.
It is a bit rude, but it is somehwat showing off and so hard to avoid if you have a nice camera.
You see someone at an event, and they have a group of people posing for a shot. They are trying to take a picture with some compact or, more often these days, a camera phone. Even more amusing if the person taking the picture has not used the camera/phone before so has no clue what button to press. Even so, they take an age to frame the shot, and get it to focus, and then delay on shutter button, maybe even a double flash to kill red-eye (by ensuring everyone has blinked and closed their eyes, or whatever).
Anyway, in the time they have composed the shot you have rattled off half a dozen shots, different angles, close up, wide angle, portrait, landscape, all done at a nice low f/2 or some such giving the background some blur with no shutter delay, near instant focus, and 18+ mega pixels. All before they have managed to work out which button to press.
I found myself doing it a couple of times at the school reunion this weekend where I was sort of unofficial photographer. Sorry.
It is clearly a bit mean. But what do we call it, apart from just "being a prick"?