Marc Andreessen is famous for giving birth to the Web browser - in the 1990s. He'd like to be famous for some newer stuff, too - like Ning, which is getting attention as one of the more interesting ideas in social networking. (It helped 50 Cent to build his fan site.) He's also become kind of a de facto brainiac commentator on Silicon Valley, mostly through his blog. Most recently, he's joined Facebook's board of directors. In a conversation with Condé Nast Portfolio's Kevin Maney Andreessen talks social networking.