Twitter's CEO fields questions at the Aspen Ideas Festival. Dick Costolo discusses his company's growth and ubiquity in recent news events. He shares his brief explanation of the Twitter and Vine platforms. Costolo shares stories of unique conversations that have happened in public, on Twitter. Katie Couric asks Costolo about his company's place in recent reports about the NSA's PRISM program, Twitter's IPO, and the "second screen" used by television viewers.