FILE- The Twitter icon is displayed on a mobile phone in Philadelphia on April 26, 2017. Tesla CEO Elon Musk won't be joining Twitter's board of directors as previously announced. The tempestuous billionaire remains Twitter’s largest shareholder. Twitter CEO Parag Agrawal tweeted the news, which followed a weekend of Musk tweets suggesting possible changes to Twitter, including making the site ad-free. Nearly 90% of Twitter's 2021 revenue came from ads. (AP Photo/Matt Rourke, File)