: We should all keep in mind that the PFDs we kayakers wear will not
: keep our heads out of the water if we are unconscious due to
: head injury or hypothermia.

While this is certainly true, if you look at kayaker drownings, it's pretty obvious that unconsciousness is not a factor in most of them. Simply having enough flotation to keep one's self at the surface where one can swim or at least actively keep one's head above water, would probably prevent the majority of drownings. In the incident cited, PFDs would have prevented the initial distress situation and prevented the would-be rescuers from getting into distress themselves.