The first-generation iPhone was activated by users at home, with the aid of iTunes. For the iPhone 3G, that process has changed. Users will now activate their iPhones, and presumably switch phone number to the new device, in AT&T and Apple Stores.
The activation process will reportedly take 10-12 minutes.
Customers won’t be required to activate upon purchase, but Apple and AT&T are reportedly looking into ways to prevent users from unlocking the unactivated phones.