Michael and Xochi Birch founded the Bebo social network in 2005 and sold it to AOL in 2008 for $850m. AOL struggled to make their acquisition work in the face of competition from Facebook and sold the business in 2010 for 1% of the price paid. Recently the Birches bought back into Bebo, and hope to show it can still find a niche. They are pictured at their home in Pacific Heights, San Francisco