Combine vastly extended interconnection with that basic feature of computers (they capture data), and the result is the beginning of a radical new possibility: that each computer’s archive of its own history becomes available to be tracked and influenced by any other computer anywhere in the internet’s vast universe of networks. Human beings themselves, as regular users of those computers and their archives, became, in principle, “trackable and tractable.” The actualization of this theoretical possibility resulted from multiple commercial innovations, spurred by various forms of necessity and opportunism. It was marketers, plagued by the perennial difficulty of reaching customers with their messages, who took advantage first with the humble cookie, capable only of tracking people on single devices, and more recently with techniques that link online data with offline behavior or use a social media ID to combine data about various online selves.

Nick Couldry & Ulises A. Mejias, The Costs of Connection, loc. 114