As hatgirl said - the problem isn't the retailers. Every eBook retailer with an online portal, from Amazon on down to the tiny and unheard of would almost certainly rather not mess with geographic restrictions. They'd pretty much prefer to sell to anybody with a viable means to get money to them. However the Publishers require them to make a decent effort to honor the Geographic Restrictions.
The problem is geographic restrictions in regards to the eBook contracts. In eBooks, the Point of Sale is considered not the store but the residence of the buyer.
Publisher A might hold eBook rights in Australia but has never bothered to actually put out an eBook. Meanwhile Publisher B holds eBook rights in the US, and is selling away. And Amazon is put in the position of telling all those Australians who manage to track down the eBook "Sorry, you aren't allowed to buy that because YOU'RE AN AUSTRALIAN!"
There are numerous threads around on tricks and tips to circumvent the roadblocks. I could tell you that if I were Australian, I'd learn them.
