StudiVZ stays in first place for almost a week now and you can read the whole story in an own encyclopedia. By the way, blog posts are 60,074 (zune, ranked 4th) to 2,912 ( studiVZ, ranked 1st), Brintey Spears made it up to 476,985.
But check the search page, the first proposal to refine your search is myspace. Thus is much more associated with blond teenagers.
Well, facebook and even OpenBC follow in this list, but the 1.3 billion dollar community seems to be the most similar network.