Facebook on Wednesday uncovered its poorly-guarded secret and filed the S-1 form needed to make an initial public offering of stock, or IPO. The company is hoping to raise a steep $5 billion from the share offering, although Facebook isn't willing to commit to a valuation on how much the company is worth. It did confirm that it had 845 million total users, about 483 million of which sign in to the social network every day.
