Jon Evans of TechCrunch zeroes in on Facebook's big problem. Mark Zuckerberg wants you to believe that Facebook was designed as a platform where anyone can share their ideas, but as Evans points out, it's Facebook's algorithm that decides which ideas you see.
When Zuckerberg talks about giving people a voice, he really means giving those people selected by Facebook's algorithm a voice. When he says "People having the power to express themselves at scale is a new kind of force in the world — a Fifth Estate," what he actually means is that Facebook's algorithm is itself that Fifth Estate.