Now that I think about it, why would the Cabal even want that sort of information on someone?
Sure, you can argue for reinforcing propaganda through matching thought patterns in groups of people, or CCP-tier tracking, but those examples don't feel right.
Cabal loves their masks right? Don't they even go so far as to tear of victim's faces?
In that regard, 'Face'-book is a bit on the nose. Who's to say that FB isn't used to track and eventually nap potential victims?
Who's to say you won't join us? Stare long enough into the Light.
[HUNTER]
Shh, don't tell them.
Possession occurs through the right eye. That's what they're symbolizing when they're doing that. That they are under that influence.