Paul:
You bucked the rivet squarely on the head: informed consent and transparency is always preferable to the alternative.
I remember every time I climb into a GA plane what my primary instructor imparted when I was starting my trip down aviation lane: by participating in this activity, we assume a certain level of risk that is greater than lying in bed all day (which, in itself, carries some level of risk that is >0) but less than standing on the edge of a cliff and leaning over. The question becomes how far do you lean over or not, and what do you do to lessen the chance that you’ll be doing a swan dive onto the rocks below.
There’s lots of good, some of it extremely dense, analysis of risk mitigation; certainly the feds have done at least a valiant effort to talk about it to the pilot/AP/IA/CFI community; but when it comes to the great unwashed lined up to take a ride on one of these spectacular birds, their view is colored by the experience of lining up at gate 21 for a trip for vacation.
It’s a matter of perception…big bird, captain and co-pilot up front, memories of movies with these magnificent machines returning home…how hard could it be, right?
Informed consent. Let’s not sugar coat it. It’s not the same. As you point out, there is no scientific data which says it’s x% worse (or better) than normal GA operations or Part 135 or 121. But, paying your donation, climbing on board a 17 or what have you, yes, you sign a waiver that acknowledges that YOU assume the risk while the organization will take all steps a reasonable man would take to be responsible for their half.