How does this work in real life? How does say Tesco can find out if I’m shopping there because of a billboard ad, or because it’s conveniently located on my commute? How do they measure their ad campaign effectiveness?
Facial recognition in stores, your credit card, or your loyalty card tie your purchase to an ID, which then can be back-tied to all the Internet surveillance in your browser and on your phone, to attribute purchases to ads viewed on-line. It's a bit tougher with attributing real-life billboard ads.
