You may have read in forums and elsewhere about the “iPhone Carrier Update” dialog presented by iTunes each time the iPhone is connected to iTunes 7.7 or later. In the past I had suggested that if your iPhone is “carrier unlocked”; not connected to one of the Apple carrier partners in your country, you should not apply this update when Apple’s dialog comes up.
The reason is because the “iPhone Carrier Update” will update settings relating to the “carrier partner(s)” within your iPhone, and if your iPhone was unlocked and your SIM card is not from one of the “carrier partner(s)” the APN settings (data settings) of your iPhone will be overridden, causing you to have to update these settings each time.
You can read other tips to know when owning an iPhone in Hong Kong by checking out my article, What to Know When Buying an iPhone 3G in Hong Kong or the more layman article 10 Things a Layman Should Know About Hong Kong iPhone 3G.
When Apple made the iPhone 3G available on the little island, Taiwan, these phones sold through the official carrier partner, Chunghwa Telecom, are all carrier unlocked.