More than 60 percent of Internet users in the United States have signed up with the site, and its presence has reached into almost every country on Earth. You might think that Facebook is taking over the world . . . if you speak English.There are, however, a few regions where Facebook has not been able to penetrate the market as it has in the West. China, Russia and South Korea have all developed their own popular variants of the idea. Japan also has its own social networking sites and the top three: Gree, Mixi and Mobage Town, are currently in a battle that has become so fierce that Facebook might not even stand a chance.