It's been three years since Sheryl Sandberg left Google's neatly indexed file cabinet for Facebook's messy walled garden. As the social giant's COO, she's propelled Facebook's mammoth tailored-ad platform and main revenue source to great success and is now talked about in other boardrooms with reverence. No, Facebook didn't need saving, but it did need Sandberg. The right hand of a 27-year-old CEO, Sandberg's experience drives the company's growth the company now claims more than 750 million users something that will prove to be indispensable when Facebook files for an IPO sometime in 2012. The company is reportedly looking to raise a cool $10 billion during the offering, pushing its valuation to a staggering $100 billion. No other U.S. Internet company has come close to hitting the $10 billion IPO mark, but then again, none of those companies had Sandberg.