San Francisco, UNITED STATES
Stone and Williams of Twitter speak on stage during TechCrunch Disrupt SF 2012 in San Francisco
Twitter co-founders Biz Stone (L) and Evan Williams speak on stage during day three of TechCrunch Disrupt SF 2012 at the San Francisco Design Center Concourse in San Francisco, California September 12, 2012. REUTERS/Stephen Lam (UNITED STATES - Tags: BUSINESS SCIENCE TECHNOLOGY)