Japan’s Softbank Mobile has added a social networking category to the top level menu of its Yahoo mobile portal. Rather than launch rely on its own social network it has offered access to multiple others: MySpace Mobile, Mixi Mobile, GREE and Avex reports Wireless Watch Japan. Softbank is the challenger in Japan, so they want to attact customers rather than focus on getting their customers to use their own services—although Softbank does partly own Yahoo Japan, so I guess it can’t really lose. TechOn notes that Softbank now has more than 10 million 3G customers.