We all know Candy Crush Saga is popular, but just how big is it? According to developer King, the game has been installed more than 500 million times across Facebook, iOS, and Android. It's so popular that, according to the studio, one out of every 23 Facebook users is a fan of the game. The news comes as the mobile versions of the game celebrate their one year anniversary. "The past year has been one of the most exciting times for King," says King designer Tommy Palm. And it's good news for a company that's expected to file for an initial public offering sometime soon, following other social game companies like FarmVille maker Zynga. However, while Zynga has seen a steady decline since going public, the slow and measured success of King means the company could very well see a different fate.