It's that way in Europe and the UK, in the US if your GSM phone get's stolen or lost, all the person finding the phone needs to do, is put their OWN SIM card into the phone ti use it.
The only thing that can keep them from using the phone is to put a password on the phone and the SIM card. But someone that knows what they are doing, can by pass the phone's password, many phones that just means resetting the phone or installing another version of the phone's OS (operating system).
There are apps/services that will allow you to lock the phone even if they change the SIM card. Smrtguard does this, but if you do not have a password on the phone it won't lock it remotely
