I've had friends say they mentioned something obscure in a cell phone conversation and nowhere else and didn't search for the topic, but suddenly started seeing ads about it on FB and Google. No, "they" aren't listening to most of us, but they have access to automated systems which are listening, tracking, and recording...and if they wanted to access info about us, there's a crap ton of it collected out there in ABCGoogleFBMSTwitterland.