@ Wasee that is why the sim should be registered. Incase your phone is stolen and upon notification to the service provider, they can send a kill command to disable the sim when someone tries to use it, or in the event it is being used in crime, it can easily tracked.
Now tracking a stolen handset is definately not easy, but with the advent of GPS technology and companies developing technology to track electronic serial numbers. The phone could be disabled making it unusable, this will deter criminals from stealing cell phones.
Also some phones now allow use of passwords, anti theft software e.t.c, i am sure crooks dont want to steal a phone and spend so much time 'fixing' it before they can redeem it. It will become increasingly difficult to use stolen phones.