This seems like an odd thing to have in Sublime. To the user, registration offers three benefits:
- No occasional nagging.
- Access to dev builds.
- The warm feeling of knowing you're not abusing Sublime's remarkably gracious evaluation trial.
If a user is pirating Sublime, they presumably don't care about (3). Revoking (2) doesn't require phoning home; new builds presumably include a list of pirated/refunded license keys. So by pirating Sublime, a user would eliminate the occasional nag message in exchange for being unable to upgrade to newer versions.
I don't doubt that a number of unscrupulous users will do that anyway, if for no other reason than they can. What I do doubt is that deactivating a pirated copy would persuade its user to purchase a license instead of simply using an up-to-date unregistered version.
On the other hand, a lot of users have very strong opinions about software that phones home unnecessarily. The idea that an existing piece of software could stop working based on the unilateral decision of a third part is very concerning to many developers. This is true even if that third party is generally trusted and well-regarded -- it adds an extra point of failure that provides no value to legitimate users.
Right now, this measure can (I presume) be easily circumvented by blocking the HTTP request on the client side. This means that an unscrupulous party distributing pirated license keys could just as easily distribute directions or a script to circumvent it. The only way around this is to require online activation, which some users would find unusable in practice and many, many more would find objectionable in principle.
I can only provide my own perspective here, along with some reasonable guesses as to how others might react. I don't know the underlying business case, and it's possible that you have information indicating that this would be beneficial in some way that is not apparent to me. But based on my understanding of the situation, I see substantial risk for uncertain benefit.