According to The Verge, AT&T is set to launch a new service meant to thwart cellphone thieves. The company will allow customers to shut down voice, data and SMS on stolen devices.
AT&T has reportedly issued information to employees on how the service will work. Customers will be required to inform an appropriate AT&T rep of a missing phone, etc. By shutting down those three services, customers will prevent the phone from being used without having to endure the inconvenience of a SIM block. This may tie into April's news of a national multi-carrier registry of stolen phones.
It's worth noting that turning off data service will presumably also knock out Apple's Find My iPhone capability, which would impair users' ability to track down their own phones. No word on cost or availability of the service from AT&T yet, but we have reached out to them for comment.
Update: Comment from AT&T's press team --
"As announced in April, AT&T is creating a stolen phone database to prevent devices reported stolen from accessing wireless networks. We will install this availability next week for AT&T phones on our network and are working toward a cross-carrier solution later this year."