You can't pirate WoW. If ubisoft made all games have the login requirements of a MMO, then you shouldn't be able to pirate them either. If ubi is going this far they should at least make sure that folks can't pirate the games. If not, it's useless.
Also, in my first paragraph, I meant to say I like how Ubisoft is treating Pirates, not PC gamers, brainfart. :P
WoW is harder to pirate because the core functionality of the game requires being online (interacting with other players, and accessing all kinds of content which is not available offline).
That's not the case for most games, such as AC2. In this case, the requirement of being online is purely for the sake of verification, hence much easier for crackers to remove (as removing it won't affect the core gameplay).
My Mario Kart Wii friend code: 2707-1866-0957