Well, one of the kindles strongest features is that it can connect to a cell network and receive documents really quickly online. Amazon has to negotiate a similar deal with an evdo carrier everywhere else for it to be available everywhere else. Not a small task i imagine.
And Kindle vs iPhone isn't a real competition. The iPhone may be a very nice generalized device, but it can't replace the kindle for reading. Specialization and focus still wins out.
Just put a GSM/GPRS/EDGE/whatever3G modem inside and let the user pay for the bandwidth. That would also make the device cheaper (you don't have to pay for the lifelong bandwidth usage of the device) and available in just about every human settlement on the surface of Earth that has phone coverage. Most carriers have an unlimited data plan available.
That Amazon removes a layer of complexity (in this case, billing) is a huge plus. If I had to pay $30/month to use the Kindle, I probably wouldn't have bought one.
Right now, Amazon has an incredible way to market the kindle. It doesn't require a computer or anything from the owner (beyond an outlet to charge once or twice a week if you have EVDO on OR once or twice a month if you dont).
This is something that very few, if any other companies can claim. Not even cell phone companies can claim this - Verizon needs AT&T or Sprint or whoever in order to allow people to talk to everyone else.
Adding wifi support removes this claim - you're now dependent on the person's ISP (internet connection), router manufacturer (provides the wifi) as well as a few other misc things. That takes away from the simplicity of the device.
Amazon could provide both a wifi and an EVDO connection. Wifi chips probably are very cheap on scale these days.
If the EVDO connection is available in their area, great. Use that. But if it is not, users can figure out how to set up the wifi connection. They have to figure out how to set up the wifi connection in their notebooks anyway.
I am an international users from Italy, and I was very frustrated to learn that apple cannot open internationals markets not only for the ability to download content from everywhere, but also because it does not have the rights to sell 90% of the ebooks outside US.
The fact that it's not available in other countries doesn't have to do with technical limitations of the over-the-air functionality since you can just download books to your computer and copy them to the device over USB.
The problem is the same as it has been for other content distribution systems like iTunes, where the publishers/other big-brother-ish entity decide what Amazon (/Apple/whoever) can do with the content.
Amazon says to pengiun books (or whoever) "We want to put your books on the Kindle." and pengiun tells them where they can go... Eventually they start convincing people -- but start throwing 'Canada' and the like into the deal and it gets a lot harder.
In short, what I'm saying is that eventually Amazon will convince the powers-that-be that the kindle is a profitable business and they'd be stupid to continue ignoring potential sales in other countries... And that's when the rest of us will get it (wirelessly or otherwise).
Actually there is some very good evidence that a generalized device for ebooks actually can win out. I'd recommend that anyone interested in ebooks read this article.
I know it's not easy, but it's not impossible either. Besides, every country with mobile coverage has one or two dominant players which means that the number of deals might be manageable. They can gain more efficiency if they reach multi-country deals with multi-national carriers such as Vodafone or (please god no) Orange.
And I was thinking the music-supporting Kindle might be an entertainment device to rival the iPods not the iPhone. Imagine a device with books and music: it would be an awesome mobile entertainment device. They already have most of (all?) the necessary hardware in the Kindle 2.
While the kindle's proven to be a big sales hit for Amazon, I think it's likely that a hybrid video/music player will win out as an entertainment device over a hybrid text/music player for most consumers
An other reason could be the need for publishing contracts for eBooks. Amazon has to provide a sufficient amount of ebooks on their marketplace to make the kindle a success.
And Kindle vs iPhone isn't a real competition. The iPhone may be a very nice generalized device, but it can't replace the kindle for reading. Specialization and focus still wins out.