MENLO PARK, CA - MAY 18: A 'like' sign stands at the entrance of Facebook headquarters May 18, 2012 in Menlo Park, California. The eight-year-old social network company listed their initial public offering on NASDAQ Friday morning at $38 a share and a valuation of $104 billion, making its IPO the third largest in U.S. history after General Motors and Visa. (Photo by Stephen Lam/Getty Images)