Excerpt from this article:
By harvesting Facebook “Likes,” the researchers’ computer model proved more accurate at divining a person’s self-reported personality traits than their own kith and kin.
…In the core part of the study, the competition between man and machine came down to who knew the subject best. But subjects don’t necessarily know themselves that well. Even though the Like-based computer model was geared toward predicting a person’s own evaluation of himself based on the Big Five [a set of personality measures that includes openness to experience, conscientiousness, extraversion, agreeableness, and neuroticism], the model proved eerily adept at predicting real-life behavior refracted through a user’s Facebook activities (e.g. number of status updates, political affiliations)—in some cases, the model outperformed the subjects themselves.