On a related note, I had a weird experience where I was talking about a trip to Vietnam with my friends. A few hours later, I saw an ad for air travel to Vietnam on my FB page.
Now I'm 100% sure I hadn't googled or searched for Vietnam previously. At first, the conspiracy theorist inside said "they're listening!" through my phone microphone or whatever. But then, I thought, could they have been forming a pattern of my behaviour over the past several days, cross-referenced across several platforms (maybe I had searched for "Travel destinations" and also a friend had given a travel recommendation of Vietnam on chat)? Have the algorithms gotten that advanced?