The Battle For Facebook

Claire Hoffman: It's a sunny afternoon in downtown Palo Alto, California, and inside the graffiti-covered walls of the Facebook headquarters, workmen are hanging lights and arranging tables for champagne glasses. Tomorrow night, there will be a party to celebrate Facebook's four-year anniversary. But in a nearby building — one of four sleek offices that the social-networking Website runs not far from the campus of Stanford University — the company's founder is oblivious to the preparations. Mark Zuckerberg, the head of the Facebook empire, sits inside the safety of a small, glass-walled office, hunched over a Styrofoam box of take-out. He looks more like a boy in a bubble than the CEO of a…