History has well-proven that if a feature can be abused, profit-seeking corporations will do so.
The ability to command shut-down is a useful feature to the RIAA, MPAA, BSA, and investigations concerned with deletion of data or ongoing theft. After determining someone is using P2P, the RIAA/MPAA/BSA could seek a court warrant to require the machine to be disabled so that the evidence cannot be deleted by the perpetrator. With business-friendly laws always being made to increase the rights of corporations (corporations are people too) versus the consumer, it is conceivable that eventually, courts will receive requests to disable the machine of someone using P2P to transfer a copyrighted work on the internet. Since nothing is "harmed", destroyed, or seized, it would need less stringent requirements than obtaining a search warrant. And if the user feels strongly about it, the user could simply file a notorized affidavit and the signed letter from an authorized inspection to have the motherboard and CPU re-enabled.
Disabling the PC doesn't need the owner to be subscribed to an anti-theft service. Such a subscription is needed only if the owner wants to have his PC disabled if it is stolen. Because the feature is always available, a court order could legitimately command any CPU and its motherboard to be disabled remotely. Eventually, laws can be changed via lobbyists or via changes to ACTA that would relax or eliminate the need for court order since it is beneficial to business prosperity to disable PCs that perform hacking, send P2P packets of copyrighted material, or are bot stations. Since no search or seizure occurs, and nothing is damaged, many concepts of the 4th Amendment might not apply especially if the law changes are implemented via ACTA. Note that once the initial version of ACTA is ratified, further changes to ACTA do not need ratification. The ACTA committee is a set of government representatives and industry representatives that meets to determine and approve changes to ACTA as a response to changing technology. It is important to note that this represents a situation where industry can directly influence both the writing and approval of laws because laws are required to be changed in order to accomodate treaty changes.