Click to view a price quote on AAPL. : The social network, famously created in a Harvard dorm in 2004, turns 15 next year -- pretty long in the tooth, in Internet years. And an increasing number of its shareholders are saying it's time for Facebook (FB) to grow up. What does that mean, exactly? If you look at a proposal filed on behalf of several large Facebook shareholders this week, it means forcing Zuckerberg to step down as chairman.