I'm back from a week at my mom's house and now I'm getting ads for her toothpaste brand, the brand I've been putting in my mouth for a week. We never talked about this brand or googled it or anything like that.

As a privacy tech worker, let me explain why this is happening. 🧵

First of all, your social media apps are not listening to you. This is a conspiracy theory. It's been debunked over and over again.

But frankly they don't need to because everything else you give them unthinkingly is way cheaper and way more powerful.

Your apps collect a ton of data from your phone. Your unique device ID. Your location. Your demographics. Weknowdis.

Data aggregators pay to pull in data from EVERYWHERE. When I use my discount card at the grocery store? Every purchase? That's a dataset for sale.

They can match my Harris Teeter purchases to my Twitter account because I gave both those companies my email address and phone number and I agreed to all that data-sharing when I accepted those terms of service and the privacy policy.

Here's where it gets truly nuts, though.

If my phone is regularly in the same GPS location as another phone, they take note of that. They start reconstructing the web of people I'm in regular contact with.