From the Financial Times:

Facebook is hardly the first company to harvest customer data and resell it. Neither does this practice always have a nefarious odour. Many of us still have a little card hanging from our key chains. It is scanned at the supermarket checkout. In return for a small discount on our groceries, the supermarket chain constructs a profile of our habits that they sell to food companies, or use for coupon offers and the like.

Notice the similarities between this exchange and what went on at Facebook and Cambridge Analytica a few years back. At the supermarket the data are exchanged for what is in effect a monetary payment. In the Facebook/Cambridge Analytica case, too, the consumer was paid for providing personal data. It was collected as part of a purportedly academic survey, where respondents were paid a small sum.

But the survey was conducted by a third party, not Facebook itself, and data about the consumers’ friends was allegedly taken too, without the friends’ consent. Once the data were gathered it was whisked off, without anonymisation, to Cambridge Analytica, which used it to tailor political adverts aimed at the specific individuals whose data were hoovered up in the first place.