I do wonder how deep Facebook's tracking goes. I deleted my old account. A couple of years later, I had to make another one to advertise a new product I'm working on. I used my real name because it was tied to my FB advertising account, but I added no friends and shared zero details except for my address (again, required for the ad account).

Facebook's friend recommendations since then have been hilariously wrong. I thought they'd just track my location or use some complex algorithm to match me to old friends. But they don't seem to have a clue about any of it.