"In perhaps the creepiest example, Facebook applied for (and received, last year) a patent for a tool called Techniques, for emotion detection and content delivery. It would use the camera in your phone to take pictures of you as you scroll through content. Facebook would then use facial analysis to measure how much you did or did not like the content in question, so as to determine what kind of stuff to send your way."

https://www.rollingstone.com/politics/features/taibbi-facebook-can-we-be-saved-social-media-giant-w518655