One of the things that really shits me about my Kindle is the fact that books from key authors aren't available to me solely because I'm based in Australia. But according to Jason Davis over at BookBee, a blog dedicated to the digital book, a highly positioned source in the Australian publishing industry told him that there is no legal reason for Amazon to offer different books in Australia compared to the US.
So if there's no legal reason for offering a different collection of books to different countries around the world like Australia, why would Amazon do it off their own initiative?
So Amazon and Co don’t see the ebook market as big enough yet to bother allowing Australians full access to their catalogue – and therefore swamp any efforts by local retailers to sell ebooks (not that by-and-large, they're bothering right now). In other words, they're restricting a section of books that Australians have a legal right to purchase merely to keep local publishers happy (they know to do so won't cost them much anyway.)
On the upside, this does mean that there's also no legal ramifications for you should you tell Amazon you happen to live in the US to get access to their complete catalogue. Or do the same thing with Apple when the iPad is released next month.