The OpenSocial platform may be being led by its biggest rival, but Yahoo is not about to be left behind as everyone-but-Facebook climbs on board the train.At Google's developer's conference last week, Yahoo's Xavier Legros made the case for developing apps for  Yahoo to a roomful of Open Social developers.Legros' pitch featured repeated references to an impressive number that makes Yahoo the player it is: home to 600 million unique visitors per month.Yahoo was one of about a dozen social networks, or "containers," for the Open Social platform who gave their pitch to developers.Look for more videos from this session later this week.And apologies for the shaky, grainy video. Most of the problem happened as people tried to get past ... [ Read more ]