Mixi

= Mixi = Mixi.jp is a popular content hosting silo and activity aggregator which is the most popular social network in Japan.

Criticisms
In order to prevent abuse, Mixi requires users to enter a Japanese phone company and number to register. Registration completion links are then emailed to the phone. This creates a requirement that a person have a contract cell phone in Japan (Google Voice or Skype numbers will not work).