You're picking Taylor Swift to make it sound your argument is solid...
Aren't there better indicators? If I follow my local city's LGBT group's FB page, well, what do you think my political leanings would be? Or on the opposite end, if I follow that megachurch's FB page? Or even if I'm just friends with many people who "checked-in" there last Sunday.
Can you point me to the online ad service where in 2004 you can do "Show this ad to people of (gender/age/race/sexual orientation) living in (area) who like (these things)"?
Also Cambridge Analytica did more than that, they figured out whether the voters were easy to influence from their Facebook profiles, and they targeted people on the fence with ads pointing to Anti-Hillary conspiracy videos...
Aren't there better indicators? If I follow my local city's LGBT group's FB page, well, what do you think my political leanings would be? Or on the opposite end, if I follow that megachurch's FB page? Or even if I'm just friends with many people who "checked-in" there last Sunday.