Dick Costolo is stepping down as CEO of Twitter after about five years. The company announced the news in a press release but provided no explanation. CNBC doesn't sound shocked, however: "Many investors and analysts have called for a shakeup amid a sluggish run for Twitter's stock," says its report. "The company has struggled to expand its user base and grow revenue through advertising and other streams." Twitter co-founder Jack Dorsey, 38, will be interim CEO until a replacement is found.
The move takes effect July 1, and the 51-year-old Costolo will remain on the board of directors. With Twitter's base of 302 million active monthly users up a relatively sluggish 18% over the last year, the Wall Street Journal reports that Costolo was trying to convince investors that they should look at the larger number of people who see Twitter's content even if they don't have an account. "His efforts appear to have fallen short," says the Journal. Shares rose sharply after the news, up 7.3% to $38.45, reports MarketWatch. (Read more Dick Costolo stories.)