You Give Apps Sensitive Personal Information. Then They Tell Facebook.

"Privacy lawyers say the collection of health data by nonhealth entities is legal in most U.S. states, provided there is sufficient disclosure in an app’s and Facebook’s terms of service. The Federal Trade Commission has taken an interest in cases in which data sharing deviates widely from what users might expect, particularly if any explanation was hard for users to find, said Woodrow Hartzog, a professor of law and computer science at Northeastern University."