Looks like they were playing tag.
Hard to tell from the camera tunnel vision, but I would have turned hard left and avoided that collision.
Reminds me of when I decided I was going to learn how to carve a circle on the slope a few years back. My plan had been to gather speed on the short steeper section and then arc left back up and all the way around to down once it flattened out a bit. Mid-way through the turn, as soon as I got pointed up, I saw someone following too close, too fast. I quickly reset edges (not weight) and made a white-pass turn to the right on my right ski avoiding the collision, but I somehow managed to get my right ski pole under my left leg. Skiing uphill is dangerous!
I've seen a few collisions where skier on the left skis into skier on the right when neither is ahead. That's the most dangerous situation, two high speed carvers skiing together.
Edited by Ghost - 11/22/13 at 7:06pm