Re: Backward Roll - Risks and benefits
I think the shihonage deaths in Japan were do to repeditive slamming of the back of the skull onto tatami - one could say that was due to ukemi skills but from what I was told it was more to a level of exhaustion and inability of those in charge (third year uni students) to spot that and more importantly stop it.
Janet may possibly correct me but the serious injury from backward ukemi was due to a collision rather than the ukemi itself although the body position at the point of collision was a contributing factor.
I've seen a few cranked necks but have never heard of a serious injury from a backward role on its own. I don't think its any more dangerous than any other form - I've already given my reason why we don't do them although I just might assign them to one of my students to loosen him up a bit.