Its funny that in the old days the main selling point of GSM/SIM-Cards were that you could physically change from phone to phone and kept your line (and contacts), now we the recent race to get things as little as possible and that virtually no one is using by default any of the extra-GSM functionalities has (contact backup), coming back to a non-physical identity as the solution (like in the CDMA days) that will force you to go to carrier every time you need to change yout phone and depend on 3rd party online services for the extra functionalities.