Behavioral data, whose value had previously been “used up” on improving the quality of Search for users, now became the pivotal—and exclusive to Google—raw material for the construction of a dynamic online advertising marketplace. Google would now secure more behavioral data than it needed to serve its users. That surplus, a behavioral surplus, was the game-changing, zero-cost asset that was diverted from service improvement toward a genuine and highly lucrative market exchange.

Shoshana Zuboff, The Age of Surveillance Cap…, loc. 255