I don't see what this has got to do with people's details.
Tesco, Amazon, and Play.com all run very similar operations where they have absolutely mahoosive databases of products, which Tesco/Amazon/Play do not actually sell, touch or handle, they just act as a directory for smaller companies to sell and advertise their products.
They all import blurb from numerous different sources and the third party retailers can tell Tesco's computers when they have a product to sell. No human involvement. Tesco spent £££££ on IT with the result that they can use their brand name and successful website to take 10% (or whatever it is) off third-party sales made via their website.