Tren Griffin works at Microsoft. He writes the www.25iq.com blog and is active on Twitter (@TrenGriffin). He was formerly a partner at Eagle River, a private equity firm controlled by Craig McCaw with investments in telecommunications and startups. From 1999 to 2001 he was vice president of strategy at XO Communications.In 1994, Griffin was the fourth person to join Teledesic, a global broadband satellite communications startup, which raised over a billion dollars at a valuation of more than $3 billion. Griffin previously worked as a consultant in Australia and Korea. He is the author of six other books, including Charlie Munger: The Complete Investor (Columbia, 2015).