No doubt Facebook has changed lives—more than 900 million, in fact. But with its initial public offering of stock on Friday, the social network founded by Mark Zuckerberg in his Harvard dorm room has raised stratospheric expectations. The 8-year-old company’s valuation would top $100 billion, according to Wall Street. Is this an omen of wild profits to come or the latest Sign of the Apocalypse? Remember the dot-com bust?