That's one of the reasons I've stuck with Sprint. As CDMA phones, their cards are hard-wired in, so if it's stolen I report it, and then it's little more than a paperweight for the thief.
Sure, there are ways around it, but it isn't as simple as swapping out a SIM card.
Now, a lot of Sprint phones (including my Bold) come with SIM cards for global communication, so not sure whether or not someone could just ignore the CDMA aspect of the card and swap out the GSM card.
Just out of curiosity.. I lost my BB, called my provider to block, got new SIM card, has been using another device temporarily until Q10 available in my country, BUT I just found out the thieve has already been using my stolen pin BB. I tried wipe the device and locate the device from Blackberry Protect but it says that it couldn't connect to the device, how so? because at the moment, the thieve is using it. I am confused..