Twitter CEO Dick Costolo to resign, 140-character limit lifted for direct messages
The company announced (PDF link) to investors that Costolo will step down effective July 1, with co-founder and chairman Jack Dorsey to serve as interim CEO while Twitter's board searches for a suitable replacement.
"I am tremendously proud of the Twitter team and all that the team has accomplished together during my six years with the Company," Costolo said. "We have great leaders who work well together and a clear strategy that informs our objectives and priorities."
Twitter has a tumultuous history when it comes to upper management. Dorsey, who led the company through investment rounds, was pushed out and replaced by co-founder Evan Williams in 2008. Three years later, Dorsey returned as executive chairman after Williams was ousted, to be succeeded by Costolo.