World of Warcraft's second expansion did pretty well. Like, 2.8 million units in the first 24 hours well. The important question is, what sort of impact did Lich King have on the WoW playerbase? What kind of impact did the expansions for EverQuest 2 (The Shadow Odyssey) and Lord of the Rings Online (Mines of Moria) have on those communities? Thankfully, GamerDNA is doing its level best to answer these sort of weighty questions by datamining the heck out of their userbase.