> some number of them will see ads related to some conversation they had recently by pure random chance. Or perhaps, they're just correlating the interests of

> some number of them will see ads related to some conversation they had recently by pure random chance. Or perhaps, they're just correlating the interests of people: 1. Person A reads about X online 2. Person A tells Person B about X 3. Person B sees ads about X, without ever having searched for it, concludes they're being spied on I'm 99.9% sure WhatsApp does this, perhaps illegally or at least grey-area.