If you think Facebook is the sole model of social games and virtual worlds, think again: With 15 million monthly users, a web-based world for teens with the odd name of Habbo is larger than most of Facebook’s top games, including Zynga’s virtual world YoVille, which counted nearly 20 million monthlies last year, but has since shrunk to nearly 9 million. Habbo, by contrast, has been growing fairly steadily since its launch in 2000. How did they do it, and what can social games learn from Sulake’s success? Read the rest here.