> you would need to swap SIM cards on the cellular-wifi router almost every time you change locations
Assuming the user can get an anonymous pre-paid service (which I agree isn't certain), why would they need to change SIMs? The cellular provider only sees an unknown person sending encrypted data to a VPN hosting service.
Assuming there selling your home address to stores you visited. If you carry the same phone to the same house every day for a month they can guess your home address.(1)
boom targeted direct mail.
Let's take this a step further, they link your phone's location to when you leave the checkout line, now they know where you live and what your buying.
(1) They may or may not be doing this, but at a technical level it would be easy.
Yes, I assume that a store could very easily link WiFi MAC addresses to CC numbers, and then loyalty cards.
The probability that someone checks out and leaves the store at the same time that you do is high. But two times in a row? Lower. 5 times in a row? Extremely small.
