> If hundreds of millions of people are spending hours on social media each week, some number of them will see ads related to some conversation they had recent

> If hundreds of millions of people are spending hours on social media each week, some number of them will see ads related to some conversation they had recently by pure random chance Another, probably more common reason that people often don’t think about is that a participant of such conversation may have searched for said product, or be otherwise profiled for it, and you might get the ad because Big Ad knows you are related to them. For example FB doesn’t need to know the contents of your Whatsapp or FB messenger messages to know how close you are to someone: how often you message, how many messages, when etc