FACEBOOK, whose users visit for an average of 50 minutes a day, promises members: “It’s free and always will be.” It certainly sounds like a steal. But it is only one of the bargains that apparently litter the internet: YouTube watchers devour 1bn hours of videos every day, for instance.

"Users may pay nothing, but companies like Google and Facebook have fixed costs to cover: engineers, data centres, etc. To make money, they squeeze their users indirectly, by charging companies to put appropriate advertisements in front of captive eyeballs. In the second quarter of 2017, Facebook eked an average of $4.65 out of each of its users by peppering screens with ads and promoted posts...

FACEBOOK, whose users visit for an average of 50 minutes a day, promises members: “It’s free and always will be.” It certainly sounds like a steal. But it is only one of the bargains that apparently litter the internet: YouTube watchers devour 1bn hours of videos every day, for instance.

"Users may pay nothing, but companies like Google and Facebook have fixed costs to cover: engineers, data centres, etc. To make money, they squeeze their users indirectly, by charging companies to put appropriate advertisements in front of captive eyeballs. In the second quarter of 2017, Facebook eked an average of $4.65 out of each of its users by peppering screens with ads and promoted posts...