After giving some space to Evan Williams and Dick Costolo, Jack Dorsey has returned to Twitter as CEO. He is—as said by The New York Times—the man who sent the first tweet:
As the man who sent the first tweet in 2006 and a product visionary who led the company in its early years, Mr. Dorsey helped make the micromessaging service into a global platform that now has more than 300 million active users, from celebrities like President Obama and Katy Perry whose tweets are followed by millions to ordinary people with just a few dozen followers.
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Mr. Dorsey was the driving force for many of Twitter’s product innovations during that time, like the ability to embed tweets on other sites, but was also a polarizing figure, firing product managers and fostering an atmosphere of secrecy and paranoia, according to current and former associates.