I'm not convinced that helmets should be mandatory for Segway-HT riders, however, I am convinced that all "scooter" riders (the inline - Razor type scooters) should definitely wear helmets, regardless of age. I've gotten hurt on one of these types of scooters and although I did not hit my head, I did injure my knee, hip and palms of my hands. If I had been unfortunate enough to "land on my head", the injury sustained could have been potentially serious.
Having said that, you could also potentially hurt your head simply by tripping on a curb, on slippery pavement (ice) or being pushed or knocked over - all starting from a standstill. While these are possibilities, we of course don't require pedestrians to wear helmets. And when they run/jog at speeds approaching 10mph - we still don't have any helmet requirements anywhere in this country (as far as I know.) So, with a Segway - which, as we know, can move you at jogging/running speeds while keeping you as balanced as a runner/jogger, there hasn't been a convincing argument that a rider would need a helmet. The argument thus far seems to be: Well, you're moving at speeds approaching 12mph and you could get seriously hurt at those speeds. Well, as I've said - so are runners and joggers.
Regarding that picture of Kamen on the front page... At that time, the Segway-HT was not "sidewalk legal" in New York yet. In fact, it hadn't even been revealed yet
So I think they were playing it safe that morning... abiding the helmet laws for NY. They were on a public corner in that photo and in a public park just before that. In the studio, I don't recall helmets being worn.
Regards,
Frank A. Tropea