http://www.washingtonpost.com/blogs/the-switch/wp/2018/03/29/facebook-longtime-friend-of-data-brokers-becomes-their-stiffest-competition/

Facebook was for years a best friend to the data brokers who make hundreds of millions of dollars a year gathering and selling Americans' personal information. Now, the world's largest social network is souring that relationship — a sign that the company believes it has overshadowed their data-gathering machine. 

Facebook said late Wednesday that it would stop data brokers from helping advertisers target people with ads, severing one of the key methods marketers used to link users' Facebook data about their friends and lifestyle with their offline data about their families, finances and health.