Yep, and then they buy your anonymized credit card history. Then they notice that a certain location trace includes a particular Starbucks that corresponds to

Yep, and then they buy your anonymized credit card history. Then they notice that a certain location trace includes a particular Starbucks that corresponds to a purchase on the anonymous credit card. You get 3-4 of these coincidences, and you can be sure that they're the same person. Then they notice that when you open someone's app, you report a particular location, and you're also coming from a particular residential IP address. Around the same time, you access a website with a particular tracking cookie from the same IP. Voila, they've got location history, a good portion of your web browsing history, and purchase history. It's fairly easy to pin this down to a name at that point. This is not a theoretical thing, it's a multi billion dollar business.