Facebook's chief executive turns 28 on Monday, setting in motion the social network's biggest week ever. The company is expected to start selling stock to the public for the first time and begin trading on the Nasdaq Stock Market on Friday. The IPO could value Facebook at nearly $100 billion, making it worth more than such iconic companies as Disney, Ford and Kraft Foods. Once Facebook begins selling stock, Zuckerberg will be expected to please a host of new stakeholders, including Wall Street investment firms, hedge funds and pension funds who will pressure him to keep the company growing. In his years as Facebook's CEO he's met world leaders, rode a bull in Vietnam while on vacation, started learning Mandarin Chinese and as a personal challenge, wore a tie for the better part of a year. Known as Thefacebook.com back in those days, the site was created to help Harvard students — and later other college students — connect with one another online. Today more than 900 million people log in at least once a month, making Facebook the world's definitive social network. Kirkpatrick, who is also founder of Techonomy, a media company that hosts conferences on the relationship between technology and economy and social progress, first met Zuckerberg six years ago. Sandberg is Zuckerberg's No. 2, the chief operating officer who oversees advertising and often serves as Facebook's smiling, public face. [...] there's Donald Graham, the 66-year-old CEO and chairman of The Washington Post Co., who serves as a mentor to Zuckerberg and holds a seat on Facebook's board of directors. Zuckerberg hired him in 2009, saying that Ebersman's previous job, helping to scale the finance organization of the fast-growing biotech company "will be important to Facebook." Not much is known about the relationship Jobs and Zuckerberg shared, but Jobs reportedly told his biographer Walter Isaacson: We talk about social networks in the plural, but I don't see anybody other than Facebook ou