Private traits and attributes are predictable from digital records of human behavior (Michal Kosinski, David Stillwell and Thore Graepel):
We show that easily accessible digital records of behavior, Facebook Likes, can be used to automatically and accurately predict a range of highly sensitive personal attributes including: sexual orientation, ethnicity, religious and political views, personality traits, intelligence, happiness, use of addictive substances, parental separation, age, and gender.