I think you're missing the point. Segway is aimed at people in densely populated areas for specific kinds of trips. I don't think Kamen is suggesting that most people would substitute it for a car all the time, only when it makes sense to do so.
For someone like me, it makes a lot of sense. I live in a big city, with bad traffic and difficult parking. I need my car for longer trips, or trips when I need to carry heavy things,. but I often go for a week without using it at all.
I walk a lot of places, and I take the train and bus a lot of places, but there are an awful lot of medium-length trips that I either don't take because it's too much of a pain to drive and park, or I take the car, which ends up being wasteful.
Segway is perfect for me in that it will give me an efficient alternative for these trips. And at least here in Chicago, where I live, and in other big cities, there are a lot of people like me.
More generally, I'm in favor of any technology which may allow us to stop being dependent on foreign oil, and there seems to be a lot of potential here, even if it only finds widespread use in corporate and industrial applications.
Why not use roller skates? They go almost as fast with not much more effort, are probably safer, and are a hellofalot cheaper.
I'm being (mostly) serious here. I do not see $3,000 in advantages in this gadget over roller skates, a skate board or an old fashioned manually powered scooter.