Most people are familiar with Microsoft's Windows Genuine Advantage program—whenever you have to "validate" Windows, that's WGA in action. Since there is no copy protection on OS X, lifelong Mac users might be unfamiliar with this whole idea. Don't worry, it looks like you might get acquainted real soon! Apple has a new patent called "Run-Time Code Injection To Perform Checks" (sounds cold and medical, no?), that's pretty much exactly like WGA. And it's all because you've been breaking promises to Apple!
So here's the deal: There's an initial check that okays software to run on a particular hardware platform. (Like OS X on your Mac.) Then there are periodic checks to make sure the software is still running on the kosher platform. If it's all shiksa, the software's execution string is stopped cold, killing the application. Vista pulls the same neat trick, keeling over if WGA says it's not the real deal (even when it sometimes is).
OS X is name-dropped in the patent app, so while it could be just about keeping it off non-Macs, this bit in the "background" section of the application's pretty illuminating, given the lack of copy protection on OS X currently:
The application owner may, of course, require the user to promise not to copy, distribute or use the application on another platform as part of the transaction by which the user obtains their copy. Such promises are, however, easy to make and easy to break.