Trading specialist Glenn Carell, who is handling Twitter's initial public offering, works at his post on the floor of the New York Stock Exchange on Thursday, Nov. 7, 2013, in New York. (AP Photo/Richard Drew)

Photo by: Richard Drew

Trading specialist Glenn Carell, who is handling Twitter's initial public offering, works at his post on the floor of the New York Stock Exchange on Thursday, Nov. 7, 2013, in New York. (AP Photo/Richard Drew)