That's a huge number and one that I honestly think signals that with sufficient value delivered, consumers will still pay for software. This might be an anomaly of historic proportions, too, though.
Blizzard said today that those 10 million paying subscribers include 5.5 million players in Asia, 2.5 million in the US and 2 million in Europe. Consider that, advertisers, when insisting that only US audiences are monetizable. Niche blog (or is it niche?) WoW Insider asks in its coverage whether Blizzard has reached market saturation. The Warcraft brand was first introduced in 1994 and World of Warcraft was launched in 2001.
For readers unfamiliar with WoW, there's a lot of video on YouTube, including the following parody of Weird Al's "That's Your Horoscope Today". It's not the catchiest tune but it's a good tour of what goes on in the game and it's been viewed more than 4 million times. When you build software that becomes a platform for user generated content all about your software - then you're in a pretty sweet spot. Perhaps that goes without saying for a company that has 10 million people around the world paying $15 per month.