Linda Yaccarino established herself as an advertising sales machine at NBCUniversal. On Friday, Elon Musk announced she’d be Twitter’s new CEO. WSJ’s Amol Sharma discusses some of the challenges Yaccarino will face at the revenue- starved social media platform.  Further Reading: - Meet Linda Yaccarino, Elon Musk’s New Twitter CEO and the Ad World’s ‘Velvet Hammer’  Further Listening: - Why Elon Musk's Twitter Is Losing Advertisers  - Elon Musk's 'Extremely Hardcore' Twitter  Learn more about your ad choices. Visit megaphone.fm/adchoices