It's said that nature abhors a vacuum, and that's true in the world of video games as well. When something popular disappears, it's just a matter of time before a replacement pops up to take its place.For mobile developers, the void in question was created when OpenFeint shut down late last year. Though not universally beloved, especially after it went through a bit of a data privacy flap in 2011, the social platform was a favorite among many game creators for the way its SDK enabled them to add social features to classic titles like Fruit Ninja and Jetpack Joyride. It was also ahead of the curve in recognizing the growing power of the Android market, adding support for Google's OS to its original focus on iOS in 2010.OpenFeint was purchased by GREE in the spring of 2011, and there were high hopes that it would continue to be available going forward. Twenty months later it was gone, leaving behind enough remorse to serve as an example of what Joni and Janet both warned people about.