It's a mistake to argue that the role of DRM is to prevent piracy. The role of DRM is to raise the cost of piracy and as a result make purchasing the game look better in comparison to consumers who would otherwise be on the borderline between piracy and purchasing a legitimate copy.
The method to play a pirated copy of AC2 atm involves jumping through several hoops. These are not barriers to a pirate who has plenty of disposable time and would never have purchased AC2 anyway. However, for the people who might have purchased AC2 anyway the pirated copy is more inconvenient than the DRM, thus increasing the cost of piracy. Arguing that this DRM has "no effect" on reducing piracy is just silly because it clearly has at least some effect, however small.
Of course this could be a net loss for Ubisoft still if rise in demand due to increasing the cost of piracy were outweighed by a drop in demand due to the inconvenience inflicted on legitimate buyers. I'm just struck by all the wishful thinking in this thread that goes beyond recognizing this outcome as plausible to instead guarantee that it will occur with no facts or data. Do any of you even have sales numbers for AC2 before you made these bold predictions?