Google's initial instinct was to disrupt Facebook with an open source play called Opensocial. Then someone at Google decided it would be better to compete with

Google's initial instinct was to disrupt Facebook with an open source play called Opensocial. Then someone at Google decided it would be better to compete with Facebook, and now we have G+, and Google has gained a major competitor. I wonder what would have happened if Google had kept iterating on an open stack. What are the leading open social stacks these days?