iThink (Want Vs Need)

I've been reading about the already legendary iPhone over the last few days and I keep thinking about how this device will actually fit into people's lives. I've concluded that the phone's real value (let's not forget it costs five hundred bucks) will only show itself to regular mass transit users. After seriously thinking about where and how people will actually take advantage of the functions (and also considering the amount of attention it requires), I've concluded it's a good tool for someone who regularly uses a bus, train or plane - anyone else is simply buying some cool for themselves. If most of your life involves traveling via car, you don't need an iPhone.

How many people will buy one, just becuse they want to play with the interface?