Do I really need Amazon to open amazon.com.au any more? The only things I really buy from Amazon are books, and since I got a Kindle, the main way I buy them is in digital format, which ships instantly over the internet. So for that, I don't need an Australian Amazon.
On the other hand, the reason I don't buy other things from Amazon is mostly the shipping costs. It's much cheaper to buy things in Australia, or from other local online vendors. If Amazon opened an Australian domain, with Australian warehouses and domestic shipping charges, I might buy more from them.
The other reason I don't tend to buy physical goods from Amazon is region-specific vendors and goods. Some things - even simple things like some lint-free tea towels - can't be shipped to Australia at all, and other goods like DVDs are only available in USA region-locked formats. An Australian operation would fix those problems.
Mokalus of Borg
PS - Come to think of it, I haven't shopped online in a while.
PPS - Perhaps my needs have changed lately.