Zoo World 2: Will this sequel breathe new life into RockYou's zoo game?

When interest starts to wane in a Facebook game, most creators will launch a big, fancy in-game feature designed to keep players coming back for more. And, it seems to work, at least for a while. FarmVille got a big boost when it rolled out a second farm set in the English Countryside and FrontierVille's upcoming Pioneer Trail expansion will likely do the same.

RockYou's taking a different tact with its zoo simulation game, Zoo World, which was one of the most popular games on Facebook about a year or so ago. Instead of launching a big add-on to the game, RockYou rebuilt the game from the ground up and launched it as a sequel -- Zoo World 2 -- which is now live on Facebook.