positional asphyxiation is quite common though it is different from sids. sometimes they get lumped in.  there's an evident difference between asphyxiation and when the part of your brain which tells your lungs to operate simply stops working while asleep (actually sids).  it really sucks. i've seen it happen to a few people and they are basically destroyed. they're just not in there after that. it's the boogeyman in the dark for anyone who has ever had a baby.
Canada