Facebook shares fell 11 percent

 Facebook Inc's underwhelming debut on Wall Street increases the pressure on the social networking giant to deliver stellar growth - a novel situation for Chief Executive Mark Zuckerberg, who has been clear he is more interested in building products than making money.

Facebook shares fell 11 percent on Monday, the company's second day as a publicly traded company, due to what many analysts and investors blamed on overly aggressive pricing by Facebook's underwriters, as well as a decision to expand the size of the offering by 25 percent.