Seems like that innocent little Xbox 360 update yesterday wasn't just to restore the option to boot the console straight to a disc. It also contained secret pirate-fighting juice.
Now that it's been mentioned, it did seem a little strange that the update came out of nowhere. And for such a tiny fix clocked in at 7mb.
But then people who had been using pirated copies of Call of Duty (both Black Ops and Modern Warfare) installed the update and found their pirated copies didn't work anymore, and it all made sense.