Twitter CEO Evan Williams Steps Down, COO Promoted

Twitter co-founder and CEO Evan Williams is relinquishing leadership of the microblogging site to COO Dick Costolo, reports the Wall Street Journal. "Building things is my passion," Williams offers as explanation for the move, adding that he asked Colstolo to take over. Adds Costolo, recently "it became clear to everybody that Ev's got to be able to focus on product strategy." The move also comes as Twitter looks to reap some sort of profitability out of its explosive growth.