TWO friends left Facebook this week after revelations that the data of 50m people had been mined and sold without the knowledge and permission of the user.

Far more is to come out of this story, along the same lines as we have already learned: that as a personal user, the information you choose to post becomes marketing data.

And that one-to-one marketing is the ultimate aim of Facebook, as it is with retailers like Amazon and newspaper publishers. The social media platform makes its money by giving advertisers as much information as it can about its users.

Facebook’s Mark Zuckerberg took several days to respond to the firestorm, and then he declined to apologise to 50m people whose data was harvested – and that of their friends – via a personality quiz.

That data was then sold to digital marketing firm Cambridge Analytica, which cynically used it to profile people and influence enough users to swing the US election for Donald Trump.

The Guardian newspaper broke the story, and rightly pointed out the nub of this story: namely, that the ‘genius’ of Cambridge Analytica was to exploit the trust of those we trust most, our friends.

Instead of apologising, Zuckerberg simply acknowledged Facebook has “made mistakes” and that it had now taken steps to make it for harder for apps to sweep up user information.

“We have a responsibility to protect your data, and if we can’t then we don’t deserve to serve you,” he said, also declining to acknowledge that the changes have only come about because of media pressure.

It’s such an issue because Facebook became an arsenal of information that was misused, and which has caused such a loss of trust among its users. Then there is the small issue of perverting elections.

Younger people had already been leaving Facebook in droves, and this story can only harm it further. “It threatens their core business model, it threatens their reputation. It has totally blown up the trust that many users have had with Facebook” management consultant Davia Temin told MarketWatch this week .

Aidan White, director of the Ethical Journalism Network goes further: “Zuckerberg’s secretive, tax dodging, click-bait empire has helped kill the dream of an internet for all. Media must find new ways to make the internet work for truth and democracy.”

But is it terminal for Facebook? Probably not, if Facebook hugely tightens up on protecting its data, monitors those extracting data and Zuckerberg acknowledges his responsibility – and not by selling off $1bn of his shares in the past two months, as he has.

While YouTube and Instagram is making big strides in working with commercial partners, Facebook is the most developed, with the best insights and ability to target specific customers.

There’s the rub. It has to persuade governments and commercial users that its motives are genuinely altruistic, and shake off the cynicism of greed that many observers – and users – now perceive is Facebook’s overriding concern.

Otherwise, as White says, the ‘dream of a democratic internet for all’ is strained to breaking point. There is little likelihood of an alternative Facebook, pure in thought and deed, reaching such scale.

And we know that: the less promiscuous social media users among us will continue to use Facebook as it works so well. I see that one of my friends is back on already.