I don't know about phone ads, but I've known for a fact that Google knows a lot more about everybody than anybody has any inkling since some time in 2010. And here's how I know:

Back then I worked as a gun designer for a small luxury hunting rifle manufacturer. One day my boss tasked me to find "innovative materials" to make lighter gun mechanisms.

So I Googled around - since Google was so good at finding shit back in the days - and found this really interesting, really obscure, niche polymer for very specialized, low-friction applications. I had never heard of it, and apparently nobody I knew who knew a lot more than I did about polymers had heard of it either. But... it was 4pm so I left it at that and went back home.

The next morning at work, I opened my inbox, and wouldn't you know it: I had an email offer from some Chinese supplier to sell me that particular plastic by the ton.

Now here's the thing: I've been paranoid about my privacy since 1999. So in 2010, I was already taking extreme measures to block trackers, browse anonymously, delete cookies at least every day, never use my real name online for any reason whatsoever and only use throwaway accounts. And there was no way in hell someone offering me this particular plastic was a coincidence.

So somehow, Google linked my search done on a Linux machine running Firefox and whatever privacy add-ons existed back then, from an IP shared by all the machines in that small gun shop, to my professional email addy.

To this day, I have no idea how they did it. Especially back then when personal data wasn't yet flying around at high speed all the time, and it was easier to figure out who or what leaked what when and where. That's when it fully dawned on me what a nefarious, dangerous outfit Google was.

I must say, they have not disappointed for the next 16 years...