Facebook–Cambridge Analytica (2018)
A whistleblower revealed that a third-party app had harvested data from millions of Facebook users and passed it to Cambridge Analytica, a political consulting firm. Facebook said the data was taken without users' meaningful consent.
Facebook apologized, changed app permissions, and faced congressional hearings.
The Federal Trade Commission later imposed a $5 billion fine and a consent order requiring privacy oversight.
Shows how data collected for one purpose can travel to third parties, and how consent decrees change corporate practices.
