I'm not surprised at all by the numbers and if you stop to think it makes perfect sense. Late BC is when more and more non gamers got into WoW. A lot of people really enjoyed BC so bought the expansion. With more people playing more people wanted to play. WotLK was hugely popular with the non hardcore crowd so with even more people playing they had high hopes for Cata, hence the very high sales numbers. Many consider Cata as the worst expansion ever and WoW lost tons of subs during it's life. It's no surprise that people who unsubbed are skeptical about the new expansion after the worst one. WoW still has the most diverse playerbase of any game. In catering to some other get upset, Cata upset people from every demographic and only those who simply enjoyed that game stayed. I think Blizz is going the right direction with MoP so far. Not perfect, but improving. If they don't mess things up we will prolly see subs increasing even more.