> I think it's true since far too many times obscure things I've spoken about appear in ads soon after the conversation

People have been making claims like this since at least the early 90s, about TV then, and no one ever credibly claims to have worked on something like this. I've worked with purchased ad data and I've never seen this data or anything that implies that it exists. It seems far more likely that its a trick of memory. You ignore most ads you see, but you remember ones that relate to odd topics that interest you.

I agree with this sentiment, people talk about x product then realise they are seeing ads for x product. Most likely the ads were there first and the people only start talking about it cause the ads have been working.

Yeah, we're well past a point where "phones" have NPUs powerful enough to locally process "sensor" input and produce decontextualized probabilties of potential interests.

It's going to happen sooner or later and people will accept it, just like they accepted training of AI models on copyrighted works without permission, or SaaS, or AWS/PaaS, or sending all their photos to Apple/Google (for "backup").