It seems like the numbers are weighted extremely heavily by those WoW subscribers. I mean, that's basically 10 million people paying $20/month right there, so that's a couple billion dollars a year that I'm sure is unequaled by the rest of the industry as a whole.
Aside from that, 15 million Steam subscribers doesn't mean that every single one of those accounts is active - it's extremely likely that a very large percentage of those subscribers just signed up with Half Life 2, or just use it to download mods/demos, or signed up a couple of years ago with the intent of using it and never did, or whatever. Point is, far from all of those 15 million subscribers are actually buying games.
Finally, how much of that PC game revenue came from soccer moms registering a copy of Bejeweled or some such?
"'Casual games' are something the 'Game Industry' invented to explain away the Wii success instead of actually listening or looking at what Nintendo did. There is no 'casual strategy' from Nintendo. 'Accessible strategy', yes, but ‘casual gamers’ is just the 'Game Industry''s polite way of saying what they feel: 'retarded gamers'."
-Sean Malstrom
