In reply to AdrianC:
Great video, thanks! Agree with Adrian's observations (and HighClimber! ). Obviously a lot depends on the condition of the snow.
I can vouch that knots make a massive difference in helping to slow or stop the fall, the first priority. They are a pain when prussiking out but it is not impossible.
Obviously having three or more on the rope ( assuming they know what they are doing ) is safer. If only a pair on very crevassed terrain it is worth carrying extra rope, for a technical route I would tend to have two ropes for the route anyway ( a half and a triple rated perhaps ).
At least the guys in the video had low attachment points. Even harder not to be pulled head first if attached direct to shoulder coils without a system to lower the attachment point to the waist.