AMERICAN BANKER - Oct 15 - Social Finance (SoFi), an American online personal finance company, is launching a social network for investors. Based in San Francisco, SoFi provides student loan refinancing, mortgages, personal loans, investing and banking. SoFi has a million members; half of those use SoFi Invest. The number of brokerage accounts has grown by 257% since Jan 1. In a recent survey, 70% of SoFi Invest clients said they discuss their investments at least weekly with colleagues, peers and family members. SoFi already has a Facebook group with 50K members.