Dick Costolo, Twitter's New CEO

Dick Costolo has been announced as Twitter's new CEO, effective today. That means Ev William, company co-founder, will step down. Why? Well, according to @ev, growth and success. More or less, anyway. "I am most satisfied while pushing product direction," WIlliams said in this Twitter post. "Building things is my passion, and I’ve never been more excited or optimistic about what we have to build."