It is not a big surprise that with over 400 milion active users, facebook has made it to pagerank 10.
Facebook has reached google. I checked it today, althought posts on the web claim that this happened around april 2010. I did a pagerank check on Seostudio.pro for google, facebook, yahoo and youtube, with the following results:
Google = Pagerank 10
Facebook = Pagerank 10
Yahoo = Pagerank 9
Youtube = Pagerank 9