Update regarding the situation here in Australia.

Stock levels from Optus, Telstra & Vodafone providers have stabilized. The initial rush has ended, and most dealers have immediate stock for all 3 models.

Optus has stopped selling pre-paid outright iPhones until further notice. Only those who have placed a raincheck and paid in full before Optus pulled the pre-paid iPhone will be receiving their outright iPhones. What this means is that buying the phone outright from Optus and paying the $80 unlocking fee is no longer possible. Whether this is a permanent move by Optus is still uncertain.

As for Telstra iPhones, it's all about luck. Telstra themselves have stopped selling no contract iPhones, but certain people have been lucky to be able to purchase the phones outright from dealers such as JB Hi-Fi. Even then, stocks for outright iPhones are said to be running low. Unlocking fee is $150, unlock usually processed within 1-3 days.

Vodafone does not sell iPhones outright.

No reason has been given about why Optus & Telstra stopped selling outright iPhones, but I suspect one of the reasons is because the phones have been emerging on Ebay.

For those who have friends/family in Australia, you could still obtain an officially unlocked iPhone if they're willing to go through the hassle of signing up to a contract, and then terminating it. The cheapest total cost including termination fees is AU$864(8GB) or AU$984(16GB) (Both by signing up to 12 Month $29 Optus 'yes' plan). It can be done, but it's a hassle. Process might take a week, even more. I've tested an unlocked Optus iPhone 3G with Maxis & Digi simcards, both worked fine.

Simply put, if you're in the market for an officially unlocked iPhone 3G, get the NZ/HK sets as soon as possible before any changes in policy might happen.

edit: added (Both by signing up to 12 Month $29 Optus 'yes' plan)