While a Polish gaming magazine reported that World of Warcraft has 10.1 million active accounts, Blizzard has since denied this.
Let's get the bad out of the way.
I've met people via World of Warcraft that I consider my friends, even years after we played together. People who I've shared with and had them share with me, because that's the secret of WoW - it's the people. It's always been, and will always be, the people you meet and play with that make the game worth playing - all the content in the world won't make you happy without people to play through it with.