Departed: June 2015
After years of trying to define Twitter, the challenge for the company proved to be a significant one — and one that, inevitably, required a change at the top. Former CEO Costolo chose to step down in June last year, handing the reins back to co-founder and original product guy Dorsey. The hope, it would seem, was that under Dorsey, Twitter could solve its product riddle. As usual as roadmaps change, so often do the executives leading them.