Apple is working with SIM-card manufacturer, Gemalto, in order to create a custom-made card that is installed in the phone.
The SIM card, which's typically a chip that carries subscriber identification information for the carriers, will be integrated into the iPhone itself. Then customers will then be able to choose their carrier at time of purchase at Apple web site or retail store, or buy the phone and get their handset up and running through a download at App Store as opposed to visiting a carrier store or calling the carrier. Either way, it reduces the role of the carrier in the iPhone purchase.
The SIM-card would work with an Apple carrier-chooser App Store app thus cutting out the need for users to call or work with the carriers, in order to get their devices all set up.
The apparent future of iPhone sales appears to be geared towards Europe as Europe has several iPhone carriers, versus one in the U.S. -- until January-ish, that work on similar cellular and data connections.