Sorry, I didn't actually address your point in my rush to be sarcastic. Mea culpa, mea maxima culpa. You are absolutely correct and I think that quadriplegics

Sorry, I didn't actually address your point in my rush to be sarcastic. Mea culpa, mea maxima culpa. You are absolutely correct and I think that quadriplegics can be used as a kind of Patient Zero for accessibility purposes, in that if you can make a widget/service/application/building that a quadriplegic can successfully use then all those other people you mentioned will probably be able to as well. It means you have to solve one problem involving extreme disability, rather than taking each disability, infirmity, and just plain old being old as discrete and individual problems. Maybe. Seems like it might work though to me.