As chief executive officer, Dorsey saw the startup through two rounds of capital funding by the venture capitalists who backed the company.
On October 16, 2008, Williams took over the role of CEO, and Dorsey became chairman of the board.
On October 4, 2010, Williams announced that he was stepping down as CEO. Dick Costolo, formerly Twitter's chief operating officer, became CEO. According to a Twitter blog, dated October 4, 2010, Williams was to stay with the company and "be completely focused on product strategy."
According to The New York Times, "Mr. Dorsey and Mr. Costolo forged a close relationship" when Williams was away. According to PC Magazine, Williams was "no longer involved in the day-to-day goings on at the company". He is focused on developing a new startup, but he became a member of Twitter's board of directors, and promised to "help in any way I can". Stone is still with Twitter but is working with AOL as an "advisor on volunteer efforts and philanthropy".
Dorsey rejoined Twitter in March 2011, as executive chairman focusing on product development. His time is split with Square (where he is CEO), whose offices are within walking distance of Twitter's in San Francisco.
In September 2011, board members and investors Fred Wilson and Bijan Sabet resigned from Twitter's Board of Directors.