The future of Facebook as an advertising platform was called into question by marketers, lawmakers and privacy activists on Monday after revelations that its data on 50 million users was harvested and used by Donald Trump's political ad firm in 2016. Facebook was already under pressure for its role in enabling fake news across its platform during the 2016 election but had mostly escaped serious consequences. Monday, however, proved different almost immediately following reports that revealed the business practices of Cambridge Analytica, which worked closely with Trump’s presidential campaign. Facebook stock fell sharply at the start of trading, finishing down 6.8 percent — a loss of more than $30 billion in value from the social media giant. Facebook went from a dorm-room project to a global media giant by offering marketers the chance to aim their ads at particular groups of people, a process known as “microtargeting.” The most recent controversy represented a legitimate threat to the company’s business model if Facebook has to make changes.

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