(FILES) In this file photo taken on June 24, 2016 Facebook CEO and founder Mark Zuckerberg speaks during a discussion at the Global Entrepreneurship Summit at Stanford University in Palo Alto, California. Facebook shares plunged March 19, 2018 as the social media giant was pounded by criticism at home and abroad over revelations that a firm working for Donald Trump's presidential campaign harvested and misused data on 50 million members.Calls for investigations came on both sides of the Atlantic after Facebook responded to explosive reports of misuse of its data by suspending the account of Cambridge Analytica, a British firm hired by Trump's 2016 campaign.Democratic Senator Amy Klobuchar and Republican John Kennedy called for Facebook chief Mark Zuckerberg to appear before Congress, along with Google and Twitter's CEOs.  / AFP PHOTO / MANDEL NGANMANDEL NGAN/AFP/Getty Images