I'd imagine that many projects moving to Gitorious/GitHub as opposed to, say, SourceForge has a role here. According to Wikipedia GitHub gained 1 million new repositories between July 2010 and April 2011. Sourceforge currently has some 300k projects. Not completely an apples to apples comparison but I'd think it gets the general idea. Technically, Git lends itself to "social coding" much better than SVN IMO.