Looks like AT&T is paying a hell lot of money to Apple since they have been the only exclusive provider for the iPhone in US since its launch. However, countries like UK and Canada are more lucky since they will be getting unlocked iPhone 4 in their countries.
Though users in these countries will still have to sign contracts with their phones, they can always exchange the SIM with another one without having to Jailbreak iPhone or unlock it. Sigh, wonder when Apple will offer a “commitment-free” iPhone 4 in the US now?
If you want to see which providers will be selling the iPhone 4 in your country, you can view a list of Official Network Providers for iPhone 4.