Retailers can also potentially resell it to other clients or even start some new lines of business themselves. From the Economist article:
If only insurers could stealthily gather a few titbits about their potential policyholders’ consumption habits. Such hints might help them more accurately target those customers least likely to make claims, and attract them with better rates. As it happens, Tesco routinely collects such information from holders of its Clubcard loyalty card. As it bulks up in financial services, that may give Britain’s largest supermarket chain an edge over traditional insurers.At risk of seeming paranoid, I think that this seems only a few steps away from the dystopian scenario wherein everyone must consciously manage their various credit ratings by weighing the impact of virtually every action, online or off. This would be a society in which you would have to hire someone to purchase booze and cigarettes for you, lest you price yourself out of affordable insurance rates. You would want to increase the density of your connections to wealthy or well-placed friends for access to better deals, and disavow those who are dangerous to your purchasing power. YOu would need to build Potemkin identities, perhaps, to qualify for various bargains or to prevent being excluded.
The distinction between public and private would complete its evolution, with private meaning "worthless data" rather than something withheld from public life, which will be a space of competing personal brands intermingling and networking with corporate ones. You would generate a steady stream of advertorial enthusiasm on various social media to secure various discounts, but live with the sense that you can't express a social self outside of that, because it would threaten the economic benefits that being a sellout has brought.
Eventually every behavior would come with an actuarial sense of its risk, determined through the mesh of surveillance networks, both voluntary and involuntary, lateral and vertical. Then we will all get to live like the caricature of Soviet-era citizens, always mouthing official platitudes while reporting on one another for political deviance out of a desperate need for self-protection. Only the platitudes we will mouth will be marketing slogans and the deviance we will report will be our own, recast as attempts at stylistic innovation.