The quandary presented by the "Delete Facebook" movement reveals the extent to which Internet users have become enmeshed in the Matrix-like world of online data. Leaving Facebook, to protest its excesses, is not all that easy, especially if an account is to be permanently deleted - it can take up to 90 days to delete everything. Exiting could affect the use of handy apps and sites accessed via one's Facebook account. And getting cut off from far-flung family members and friends, who are part of Facebook's 2.2 billion users, can be irksome when alternative platforms do not appeal to individuals. It can pose practical problems too for non-users, when an employer or a landlord relies on Facebook profiles to do checks, and organisations use it to schedule meetings and to create and manage events.

Social media giants have indeed become deeply embedded in people's lives, and the power that lies in their hands was bestowed on them by users themselves. Lured by the conveniences and diversions offered, people voluntarily surrendered considerable personal data to these companies in many cases. In others, they were egged on by apps to release their contacts. Consequently, Facebook and app owners can produce "shadow profiles" of even non-users, created by scrutinising information given by their friends and other sources. That is how the voter-profiling company at the centre of the latest data scandal, Cambridge Analytica, could obtain dossiers on 50 million Facebook users from a profiling app downloaded by just 270,000 people.