Interestingly, it is MIXI CTO http://mixi.jp/show_friend.pl?id=1 and id=2 is its president http://mixi.jp/show_friend.pl?id=2 . Obviously, the Word of Mouth (WOM) spread from these two guys, via invitation after invitation after invitation.
By the way, the face of mySpace Tom immediately becomes your friend upon signing up with mySpace: http://www.myspace.com/tom
While Mixi is by-invitation only and mySpace is free to join, seems the key persons at MIXI and mySpace are equally open and friendly to its members. It is interesting to see how mySpace will tailor its openness and friendliness to Japanese SNS market and generate WOM, when they will enter Japan’s SNS market (via Gen Kanai blog) this fall with the 50:50 partinership with softbank.