[taneq]

> but this seems like a poor example

In fact this is a perfect example of how NOT to do purchase-history-based suggestions, which unfortunately also seems to be how most companies do it. They see a big purchase (or search terms relating to one) and spam you with options for that purchase. But if I just bought a car, or a drone, or a laptop, then the last thing I want to see is ads for other cars or drones or laptops.

Even applying just a little intelligence and showing ads for accessories (floor mats? spare batteries? bluetooth mice?) would make things substantially more useful.

[heurist]

I used to see that a lot on Amazon. I just bought an electric toothbrush, why would I buy another? Haven't been shopping much lately so not sure if it's gotten any better. My example is from last year, and I remember mentioning this problem in an interview with Amazon 6 years ago, and I'm sure machine learning has been involved for longer than that. It's still easier to screw up a machine learning model than SQL.

[perl4ever]

How about if you can identify a smart phone in proximity to a store display, and later target ads at that user? That would get you a lot of people that didn't buy a product, but demonstrated interest in a category. I suspect someone has already figured out how to make this happen, but I haven't found explicit confirmation.