I think Orwell might have something to say about that. Or at least, the people who (thought they had) bought his books from Amazon might:

http://news.cnet.com/8301-13860_3-10289983-56.html

Until such time as the killswitch is abused, this remains a slippery slope argument with no basis in reality.

The trouble isn’t just this particular killswitch. As jaysonelliot was suggesting, the really insidious problem is the general trend that even when you think you’re buying a permanent copy of a knowledge work, you are often not getting what you think you’re paying for any more. I’m not sure which is worse, the dubious business models or the fact that the simplest of commercial transactions on-line routinely comes with absurd amounts of legalese attached, but neither is a welcome development IMHO.

I’ve never personally been the victim of an app store revocation, because I saw that one coming and won’t spend my money on unsafe purchases like that. But I’ve certainly seen the damage of phone-home activation, after the boot drive of my main workstation failed. Two pieces of high-end professional software, both legally purchased on physical media by my own company (each at a four-figure price), were at risk from this. It took weeks of chasing the software companies to get the licensing/activation concerns resolved, during which time one piece of software was unusable and the other was reportedly at risk of shutting down any time. It even turned out that both of those companies had completely screwed up the registration and thought my company’s licence keys were registered to someone else, and we really did get to the point of my sending them photographs of original invoices/packaging/serial numbers in one case.

In my country, hacking into someone’s computer and causing that level of damage would surely be a criminal offence under the Computer Misuse Act. I believe that remote blocking of legitimately installed software by, for example, phone home activation/DRM schemes or post-sale deletion by an app store should also be considered an offence. After all, the end result is much the same. I’ve never had the chance to ask a lawyer why it isn’t (or maybe it is, perhaps even under the same legislation, but for whatever reason the culprits aren’t being prosecuted). And if it can be a criminal offence in various jurisdictions to circumvent technical measures in order to do otherwise perfectly legal things with a copyrighted work you’ve bought (OK, “licensed”, but while I appreciate the need for lawyers to be precise, we all know how most people are going to understand the transaction), I don’t think it’s unreasonable to make it an offence to abuse such technical measures from the other side as well. Maybe we should have some sort of safe harbour provision to protect companies who genuinely make an innocent mistake but correct it immediately on notification, but the basic principle that abusing remote deactivation is illegal seems only fair.