Twitter chief executive Dick Costolo to step down

Twitter chief executive Dick Costolo will step down on July 1, and hand the reins over to Jack Dorsey, Twitter's co-founder and current chairman of the board. The company announced that Dorsey will serve as interim chief executive while Twitter looks for someone to fill Costolo's position. Costolo has been Twitter's chief executive since 2010; before that he was the company's chief operating officer. He has been criticized since taking the company public in 2013 for failing to ignite growth and find effective revenue streams for the social media company.