That old bugbear, Digital Rights Management (DRM) has been with us longer than you might imagine. Big companies have been attempting to control how we use and share media as far back as the 1890's when they tried to prevent the rolls from those old automated player-pianos being copied.
Nowadays its music and game pirates that the producers fear and they've been to some interesting lengths to stop them, and sometimes the rest of us, from being a little too generous with our their media. Imagine one chap's surprise when he couldn't transfer a game across from his Nexus One to his new Galaxy S, and who was then told by the developer that he would have to buy it again. And again, if he ever dared consider getting another phone in the future. Because the game was licensed to the phone not the user and that made it nontransferable.
Thankfully this has since been rectified and the company have now changed their DRM policy to be a little less clingy. I say thankfully because the Developer in question is the excellent French company Gameloft who brought Assassins Creed to my phone, and for that alone, I love them.