I think the problems with click fraud are orthogonal. They're a different domain with different characteristics and different solutions.
Facial recognition has been deployed to combat shoplifting [1][2]. Amazon Go is a store built around not needing to check out at a register at all. Microsoft offers Azure Kinect [3] as a way for retailers to track people moving through a store. There's no shortage of companies purporting to use AI to analyze in-store video in real-time to analyze customer behavior [4][5]. There was a video shared on this site a few weeks back showing a coffee shop tracking both customers and baristas [6] (more discussion there, including some skepticism).
I'm speculating that if they can track you in the store and build a profile on you that they'll be able to track your cash purchases. I don't think it's a terribly large leap to tie into their point of sale terminals but I don't know if any retailer is currently doing that or even planning to do that.
[1] -- https://youtu.be/g5Xf9Y6-RS4?si=De7EZTyVD66BQPeG
[2] -- https://www.nytimes.com/2023/06/28/technology/facial-
recognition-shoplifters-britain.html
[3] -- https://azure.microsoft.com/en-us/products/kinect-dk/
[4] -- https://viso.ai/features/
[5] -- https://twitter.com/jowyang/status/1214657642313871360
[6] -- https://news.ycombinator.com/item?id=37186806
