Buy whatever phone you want and then use it with whichever service you want - a man can dream. This dream, however, may soon become a reality... in Japan. The government has launched a review of the SIM lock technology that prevents simply swapping SIM cards with a separate carrier. The proposed legislation will not be applicable to the use of international sim cards.
In the United States, you are able to swap SIM cards if the carrier runs on the same type of network, but ATT and Verizon run separate, incompatible networks. Simply put, it is impossible to run an iPhone on Verizon regardless of how much hacking you do on it.
A [fairly] simple work-around for the Japanese carriers would be to remove the inclusion of SIM cards altogether, tying the phone itself to the account much like Sprint in the United States. This allows the carriers to still lock people into a contract, based off of the phone alone. Tread softly, Japan, for you are treading on my dreams.
