Facebook’s tracking stretches far beyond the company’s well-known targeted advertisements. And details that people often readily volunteer — age, employer, relationship status, likes and location — are just the start. The social media giant also tracks users on other sites and apps. It also collects so-called biometric facial data without users’ explicit ‘opt-in’ consent, and helps video-game companies target ‘high-value players’ who are likely to spend on in-app purchases. The sifting of users gets into personal — even confidential — matters.
Details may be found in an article by Natasha Singer in the New York Times at: https://www.nytimes.com/2018/04/11/technology/facebook-privacy-hearings.html.