https://i.imgur.com/WkPj5Gb.png
I've had someone tell me they visited a shopping site once and without giving the company any information, they got an e-mail from that company a day later. I told them it wasn't really possible (from just the browser's perspective) and that they must have been tracked through some 3rd party cookies.
Apparently that was false and it's totally possible for a site to use one of these APIs and instantly get your full name, phone number, e-mail address, and physical address just by looking up your IP, and then track you across "switching carriers, changing phone numbers, upgrading devices, and replacing lost devices". Scary shit.