The author means universal in the sense of a universal remote control, not universal adoption. Also, a big chunk of that 40 million is iPod Touch owners, who are not subject to carrier lock-in.

The point is that it is a sufficiently generic and popular platform that many companies that might once have rolled their own hardware have diminished need to. If the platform supports what they need and they can make do in a market of 40 million (and growing), why not? For consumers it is the same way; why buy a device when you can just download that functionality? It raises the threshold of utility.

The market doesn't have to be universal, it just has to be big and and consistent. Right now the iPhone is the only platform that can claim to have both of those qualities.

Totally agree. I don't have an iPhone (can't afford a data plan at the moment) but want one. Something feels wrong about being locked in to any one carrier for service though. My main PC isn't locked into anything. As long as the market I live in gives me choices of internet service providers, I get to choose. Does anyone know if we'll see a more open environment in cellphone service (data, voice, etc) in the near future?

Very true. It's a huge hinderance. However, the international audience of the device cannot be ignored. Neither can the huge base of iPod Touches.

AT&T lock-in is only a problem in the US, remember. Here in Australia the iPhone is available from 4 different carriers (Telstra, Vodafone, Virgin and Optus) and the fifth carrier offers plans for unlocked phones as well.

It's my understanding that you can buy an iPhone without a contract, it's just ~$600 more expensive. Visual voicemail is right out on other carriers though. 3G might work though, depending on your carrier.