Reid Hoffman (Greylock Partners)

Silicon Valley's elder statesman has had a hand in creating nearly every lucrative social media startup. The original social network--a dating service called SocialNet back in 1997--was Hoffman's handiwork. After leaving PayPal in 2002, Hoffman founded LinkedIn while moonlighting as an angel investor in some 80 startups. Among them: Facebook, Zynga, Digg, One Kings Lane, Ning, Nanosolar, Flickr (sold to Yahoo), Last.FM (sold to CBS), Six Apart (sold to Say Media), Vendio (sold to Alibaba)