What, The Fuck. Ubisoft? The one-time-registration DRM was a very well received change over the always-online bullcrap you had before. Does Ubisoft ever listen? They were actually praised for doing that.
I pre-ordered Assassin's Creed: Brotherhood back in May via Steam, and when it came out, I just registered my copy of the game once online, then I could play the game freely, even when my third-rate Internet connection's down times. Whenever I couldn't play an online game with my friends because of a network cut, I could just fire up ACB and continue playing through the gripping story, that got me occupied for some weeks.
Well, guess I'll just have to wait for a patch for this DRM bullcrap (like the ones that came for Assassin's Creed II and Splinter Cell: Conviction), and when the game goes on sale, for Christmas, maybe.