From what I've read, CA wasn't Facebook's customer. CA bought the data from a researcher who was authorized to slurp the data.
I wonder how FB views public scraping. Shades of webcrawlers.
Dr. Kogan built his own app and in June 2014 began harvesting data for Cambridge Analytica."
https://www.nytimes.com/2018/03/19/technology/facebook-cambr...