Facebook is expected to file its IPO this week, which could set several records if the company is valued at $75bn- $100bn. A $10 billion Facebook offering would rank fourth among IPOs for U.S. companies, behind Visa Inc., General Motors Co. and AT&T Wireless.  It would also rank Facebook as the biggest U.S. Internet offering ever, replacing Google Inc., which raised $1.9 billion in 2004 at a $23 billion valuation. At a $100 billion valuation, Facebook would be worth about the same as McDonald's Corp.