This book https://www.amazon.com/Aisles-Have-Eyes-Retailers-Shopping/d... goes into quite a bit of detail about various techniques retailers use to track customers.

Personalized pricing, with great details described how it works in retail in era of face recognition, mobiles, web tracking,loyalty cards, data mining etc.etc.

Recommend the read to anyone

The Aisles Have Eyes: How Retailers Track Your Shopping, Strip Your Privacy

[0] https://www.amazon.com/Aisles-Have-Eyes-Retailers-Shopping/d...

Not Google specific, but some good reading on this topic came out in January - The Aisles Have Eyes: How Retailers Track Your Shopping, Strip Your Privacy, and Define Your Power [0]

[0] https://www.amazon.com/Aisles-Have-Eyes-Retailers-Shopping/d...