NEW YORK, NY - NOVEMBER 07:  (L-R) Twitter co-founder Jack Dorsey, Twitter co-founder Biz Stone, Twitter co-founder Evan Williams and Twitter CEO Dick Costolo pose for a photo after Twitter's IPO on the floor of the New York Stock Exchange (NYSE) on November 7, 2013 in New York City. Twitter went public November 7, on the NYSE selling at a market price of $45.10, with the initial price being set at $26 on November 6.  (Photo by Andrew Burton/Getty Images)