I would probably use an iPhone mostly in the UK (and Europe) even though I don't spend a lot of time there. So it would make sense to buy one in the UK. Except, while I can easily buy an iPhone I cannot enter into the O2 contract because I don't have a bank account in the UK. It is for this reason I have a UK (Orange) pay-as-you-go SIM card rather than an Orange "plan".
So the logical thing to do would be to unlock the iPhone and use the Orange SIM card, retiring my existing cell phone for use with my Congo SIM, also pay-as-you-go.
The problem with unlocking is that future firmware upgrades will render the phone useless. If I decide to upgrade, that is. The experts in Pointe Noire (where unlocked phones are available at a price) tell me that firmware upgrades are simply devices to stall the boom in unlocking iPhones. That may be true but we all know that firmware upgrades often contain improvements, the recent Apple TV upgrade being a very good example.
A report today confirms that a lot of iPhones in the US must be unlocked as they are never activated. Apple doesn't seem to be too worried about this - they make money selling the device, after all.
The long term question is that eventually those phones which were sold at the outset and activated will come off contract (18 months, I believe) so presumably they will be legally unlockable at that time. Perhaps then the whole question of firmware upgrades will be history.
But there is also the possibility that Apple will recognize a parallel business model for those of use who want, no, need, an unlocked iPhone. World travelers with multiple SIMs would benefit enormously from such a business model (At the moment I carry four SIM cards with me, all pay-as-you-go).
Rumors are strong that the 3G iPhone will soon appear. At that time I plan to buy an iPhone and unlock it. But should I? I should probably ask this question to the nice people at Exeter's new Apple Store!