Sex Workers: Clients Are Seeing You On Facebook, Here’s How To Stop It (2015) (redlightlegal.org)

Admittedly this submission is a bit weird, but I think it illustrates some of the unintended consequences of all this incredible data mining we're being told all the time isn't hurting anyone.

There was something very similar recently as well https://news.ycombinator.com/item?id=12388370 'Facebook recommended that a psychiatrist’s patients friend each other'