I have often wondered the same thing. I suspect it's the same hostility that was exhibited at the automobile's invention (not that I think the Segway will gain as much acceptance as the auto).
Some people are either afraid of or just plain hate CHANGE! Or maybe because the initial costs are so high, people think only the rich can afford one, so for some it is a class envy of sorts.
I think these high tech thingys are facinating!