[AT&T, Rogers, Bell, Telus Samsung Galaxy S III] tamanaco:
I'm not an expert on this field, but these are the questions that come to my head as I think about the logistics to support a kill switch. I'm probably wrong in some of the assumptions that I'm making here. Please correct me if I'm wrong.

Telcos don't have an incentive to make this work. It has always been possible for a Telco to disable an IMEI at their end thus making any particular IMEI unusable in their network. They already do this when you call them to report your phone stolen. If a worldwide database of stolen phone IMEIs existed then Telcos could have the ability to disable any IMEI in that database. The issue is... who would be responsible for maintaining such database and for the problems that will certainly come up due to inaccuracies and timing of updates (Telco, Government entity, phone manufacturer or a third party) . Can the maintaining entity monetize the overhead of maintaining and supporting such database? Who would pay for it? Who makes the final ruling to include or exclude an IMEI? The end user?... I doubt it. Where would the master database copy reside? And of course... would Telcos in all countries support it? Remember, the Telcos make money off any phone that is active in their network (stolen or not). All they care about is that the user of any active phone in their network is paying the network usage bill. For Telcos the more IMEIs that exists and that can be connected to their network... the better.

I can think of a bunch of issues that could come up when the end user is able to disable the actual phone. I doubt the user would be able to disable the IMEI remotely unless they own the phone and the telco allow it. The issue in the US is that a lot of the phones are subsidized (owned) by the Telco for the duration of the contract. So, in the case that the phone is subsidized the Telco should also have the right to trip the kill switch. I'm assuming that the phone kill switch will be tied to a password known to the rightful owner and "maybe" the renter. The password will render the phone unusable unless the correct password is entered. I'm assuming that if a phone on contract is stolen then the user would either contact the Telco or trip the switch via the Internet. (Lookout and other apps do something similar remotely, but they only wipe the phone.. they do not disable it) If the Telco also has the ability to disable the phone then if the bill isn't paid not only will they disconnect you, but they will also render your phone useless. Good bye data and apps. I also assume that the ability to trip the kill switch remotely would also depend on the network on which the phone is connected. The IMEI (physical address) is translated to an IP address when using the Internet. If I steal a phone in the US and keep it turned off until I register it in a Telco in another country how will the owner trip the kill switch as only the Telco would know which IP address is associated with the IMEI.....

Gotta go to work... Given that I don't know how the kill switch will actually be implemented I don't know if any of the stuff I just wrote above is relevant or makes sense. Just curious as to how the kill switch would work.