In the case where you add someone on Facebook, Twitter, etc. and mutually follow each other without really knowing the other person - maybe they looked interesting, or said one comment you found amusing - but never followed it up with an actual conversation. Turns out the person posts quite a bit, and you end up learning huge amounts of intimate detail about their life - indeed, almost feeling like they're a close friend - even though you never actually talked.
"Oh, I followed her years back and now I know how many cats she has, what her favourite TV shows are, and when her grandparents died. She's my swant."