Twitter has made co-founder Jack Dorsey the company's permanent CEO, for the second time. He'll also keep his CEO role at the mobile payments company Square, which he founded in 2009. He joins a small group of people who have run two companies at one time.
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Steve Jobs ran both Apple and animation studio Pixar. Like Dorsey, Jobs was ousted from the company he founded and later returned as interim, then permanent, CEO.
Carlos Ghosn is CEO of Japan's Nissan and France's Renault, both carmakers. He also set up the Renault-Nissan Alliance, a strategic partnership between both companies. Similarly, Dorsey has tried to build bridges between Twitter and Square, including a service that lets people on Twitter donate to political campaigns through Square.
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Elon Musk is CEO of electric car maker Tesla and rocket company SpaceX. Like Musk, Dorsey will face questions about how he divides his time between the companies, said Jeffrey Sonnenfeld, a professor at the Yale School of Management.