I'm happy about this. One massive problem I've had with adopting eBooks, a technology that I'm really excited about, is a fear of "platform lock-in".
Let me explain. Say you buy an eBook device. It doesn't matter which one. Kindle, iPad, Sony eReader, whatever. Now you can only buy books from a single provider. And if that provider goes out of business, or if your hardware becomes obsolete, you might lose access to your books.
I have an iPhone and a Barnes & Noble nook. I almost never use the nook. I've only gotten free books for it. It was a Christmas present (or an unmentionable solstice cultural observance present for those of you who go into seizures at the mention of Christmas). I'd hoped to be able to read pdf files on the nook, but most of them don't format properly which renders it nearly useless.
Any Barnes & Noble books I buy can be read on my PC and iPhone. But still, Amazon has a better inventory, and often better prices, so when I buy eBooks, I buy them from Amazon.
Also, Sony books can also be read on a PC, Mac, iPhone, iPad, etc. But still, Amazon has a better inventory with better prices.
I'm convinced that the hardware eBooks are read on is a secondary factor. What matters most is content. Who has the best content, at the best price, with the best way to avoid obsolescence? So far, in my observation, the winner is Amazon.
Which is why I was happy to see Jeff Bezos' (founder of Amazon) quote in this blog post. Despite providing their own hardware (Kindle), Amazon is still committed to delivering content (books) as far and wide as possible. Even though I have a competing device, most of my purchased content is for Kindle, which I read on my iPhone and computer.