> Do you think Best Buy assigns cash serial numbers to individual products they sold, by default, always?

No but when you took that cash out of an ATM, it logged the serial numbers on the bills it gave you. Then when Best Buy deposited that cash at the bank they again scanned that serial number and can make an assumption that you spent that money at Best Buy.

What that information is used for, who knows? But the flow of cash is definitely logged somewhere, for some reason!

I'd never thought of ATMs scanning the serial numbers of cash, but that makes sense. However, and maybe this isn't leading practice, but stores just seem to put cash in a collective cash drawer, so they can't exactly tell what cash was used for what (though cash purchase would be rare these days). Are there regulations around logging serial numbers now?

Commercial banks don't usually share consumer info with each other. Unless it's the same bank, they're probably safe. Plus, there's no way to obtain a network-connected SIM with cash, so all of this is moot.

Ah, but that is far less critical than having your name and device IMEI show up in some database by default!

But yes, your bank could know you were at Best Buy, maybe.

You're over thinking it. You can determine this with much more available data, though you'd need to do this through aggregate. In one sense it is simpler, but in another sense it is more complex.

If you have knowledge of a withdrawal and even a rough ball park of that amount, then you can probably determine it was a phone purchase. If you're a big company like Google or Facebook, you're going to be pretty good at that regardless of the prior knowledge (which then can be back inferred). The tracking is not just limited to what information your phone sends out but what information other devices get. It's good to mix up your fingerprints and all that, but this only goes so far.

The social graph is a pretty critical tool for those doing the tracking, and that graph isn't just composed of other humans. Every device is constantly talking to every other device. Snoop on your radios and look at what they're doing. Things like WiFi and Bluetooth are constantly pinging things around you and this can be used for tracking if you know where certain MAC addresses are physically located. This won't work anymore, but like 15 years ago Samy Kamkar made a tool to do exactly that[0], because while they were mapping the streets they also recorded all the SSIDs, MACs, and whatever else they could get. So if you have a device like a router that is constantly connecting to something that's saying it is a phone, and you can see that that device is at a location at specific hours and you can reidentify someone by that. Especially when a device that normally fit a pattern stops fitting that pattern.

I mean some of this sounds crazy but I feel like 10 years ago we had more posts and conversations about things like [0]. Where people were doing things like tracking their friends' sleeping schedules[1], exploiting Facebook ads to microtarget and prank your friends[2], or spending $1k to geolocate your friends[3]. While it's become more difficult to exploit this information from the user side, the capabilities haven't gone away. They've only grown over the last decade and been placed behind more expensive walls. Funny enough, it is a time of the internet I missed. These things were fun, scary, motivating, and made us talk more openly about the implications of surveillance capitalism. We've only just become used to it, while the severity has significantly magnified. I mean when I deleted my Facebook account in like 2016/2017 I did a takeout and found that they accurately were able to geolocate my photos to where I was standing inside a specific room of my house, by aggregating the GPS information with the WiFi information (you have neighbors?).

I feel like we need to bring these conversations back. But I'm not sure how best we do them while being productive and not turning towards apathy. No one's going to kill the beast overnight, but I want to stress that it's at least better to reduce exposure. Apathy tends to come from the interpretation that it is binary. You're either fucked or not, and we're only fucked. But there's a big difference between a floor covered in shit and being neck deep in shit. I don't want to be in either situation, but if I had to choose then that's a very easy situation. It's also easier to clean up. So I guess... can we get more people to start normalizing things like Signal and Firefox? Or pick some other tools, I don't care. But encrypted communications and non-chromium based browsers (sorry Brave and Opera) do a lot to help. At worst they send a signal to these big companies that we care. Maybe all they see is money, but they'll care about your privacy if it is more profitable than not caring. They go with the tides, even if they don't really believe it. So they can be reigned, but people mostly don't know how to send a signal.

[0] https://sa.my/androidmap/

[1] https://medium.com/@sorenlouv/how-you-can-use-facebook-to-tr...

[2] https://ghostinfluence.com/the-ultimate-retaliation-pranking...

[3] https://www.wired.com/story/track-location-with-mobile-ads-1...