When I worked on commission and my task was to capture photos of the atmosphere and general development of several dance classes of one and the same dance school putting together a large, one-hour project in the end, I had to be in their rehearsal room with them, trying to be as unintrusive as I could possibly be, since their work had to go on as is I had NOT been there, and I had to be QUICK. I had to very, very quickly get an idea of both the music AND the choreography their teacher had developed for them, so in the end my photos would express clearly their ideas, postures, facial expressions, movement and whatnot (all that goes into dancing, you know).
Given the fact that I had to be so quick, and taking your definition of snapshot into account, all I ever took in those 8 sessions that accompanied with my camera were SNAPSHOTS.
They ended in an exhibition called "Practised 1000 times", and it were exactly 1000 photos - or, if "not planning", "just pointing and shooting" is the definition for snapshot - nothing but snapshots.
Where they only snapshots?
I am not sure.
It was "spur-of-the-moment"-photography, since nothing else would have worked. There was NO CHANCE to repeat a scene (other than when the dance teacher had them repeat something because it didn't work out the first time), they never posed for me, either, as in: stop in their movement and wait for me to get ready.
The room was a gym, so I had no choice of nice or neutral backgrounds. I had to make do with what light there was, and most of all be very quick. All the time.
Was I taking nothing but snapshots?
http://www.thephotoforum.com/forum/showthread.php?t=84662