Maybe they were getting this from some ad networks like Taboola or Outbrain - but then those networks don't usually have enough info to really identify you.

Sure, if they were giving your IP to a telCo who can map your IP to a name if you're a customer - that's identifying you.

It's HIGHLY unlikely this happened at the usual suspects (FAANG).

You think it is highly unlikely that Facebook/Meta is selling granular user data?

Yes, it's incredibly unlikely. So unlikely that it's basically impossible.

They explicitly and unambiguously deny doing it; if that was incorrect, there would be a huge regulatory and public backlash. (Think of what happened with the Cambridge Analytica case, despite Facebook's hands being pretty clean on that). No disgruntled ex-employees blew the whistle on this but did on other issue), which suggests it probably didn't happen.

Selling ads is very profitable. Selling data directly risks that business for little gain. In addition to the backlash when that data selling were revealed, it risks somebody else using the data sold by Meta to outcompete them on ad targeting.

>They explicitly and unambiguously deny doing it; if that was incorrect, there would be a huge regulatory and public backlash.

Companies typically don't admit to the public when they're engaged in unethical practices. Purdue Pharma is a good example.

Then you say nothing on the subject, or say something that's technically true but ambiguous and easy to misunderstand.

> it risks somebody else using the data sold by Meta to outcompete them on ad targeting

Bingo. They're unlikely to be selling the data because those data are their secret sauce. They are as economically incentivized to build sociopathic models on you as they are to keep your data out of anyone else's hands.

Even economically, it seems unlikely they would. The data is their moat and it's what they can use to target people with ads. Selling it seems counterproductive.

It was probably adtech companies.

There are a bunch who basically pay apps to use their api and then take the data.

Apple was right to kill that imho. IIRC that was foursquare's pivot

There is also lot/lon in programmatic bid requests, but I don't think they're super accurate or granular and lots of fraud. (could be wrong, just from my small experience buy side using DSPs seeing lots of lat/lons being smack in the middle of a city)

[1] https://www.safegraph.com/guides/mobile-location-data-provid...

[2] https://developers.google.com/authorized-buyers/rtb/geotarge...

[3] https://fixad.tech/wp-content/uploads/2019/02/3-bid-request-...

Many free wifi places will track and report movements with the wifi area. Using bluetooth in addition. Shopping malls in particular can use this to find where people congregate.

Can probably be related to email addresses too, and hence shared with every other mall with same ownership as well as the company that provides the free wifi.

e.g. Aruba, Meraki, ...