A public apology by Zuckerberg has failed to quell outrage over the hijacking of personal data from millions of people by Cambridge Analytica. Facebook and psychologists who have worked with it are grappling with their "Oppenheimer moment", experts say, over revelations that its data may have been used to help elect US President Donald Trump.
The scandal over the way Cambridge Analytica obtained personal information to try to manipulate US voters "is the most important moment that Facebook has faced since it went public (in 2012)," according to Professor Andrew Przybylski of Oxford University, one of the world's leading authorities on social media psychology.
He compared their reluctance to admit the destructive potential of social media to the epiphany of the father of the atomic bomb, Robert Oppenheimer, who declared, "Now I am become Death, the destroyer of worlds."
"With Facebook we have to acknowledge we are giving Frodo the Ring," Przybylski told AFP, referring to the object in the Lord of the Rings which confers absolute power.
"If you gave me the Ring I would be corrupted.
"It is not that what is happening at Facebook is by its nature bad," he added. "It is that they are using our data for products and services, but that we have no idea what they are up to."
He called for regulation and a new "ethical framework (to ensure) that users' rights are protected and that research is being done transparently and in the public interest."
Przybylski said similar crises had led to the establishment of ethical standards in other areas.
'Facebook sense threat'
"Chemistry had this moment after they invented dynamite and chemical weapons, physics had this with nuclear weapons," he argued.
Facebook and "others have been built on the shoulders of academic research... The key issue is trust. Facebook works one-on-one with psychologists and researchers and there is a fundamental asymmetry there."
Przybylski, who has spent the last two days at Facebook's San Francisco headquarters, said he told founder Mark Zuckerberg's chief of staff "Chris Cox all this to his face", and set out proposals on how Facebook might change the way it works.
"I am optimistic. They are receptive, they have a sense of the threat and they have a proactive mindset," said Przybylski, who no longer uses Facebook himself.
But Google researcher Francois Chollet has his doubts.
In a series of scathing tweets this week the inventor of the Keras open source library said "the problem with Facebook is not 'just' the loss of your privacy and the fact that it can be used as a totalitarian panopticon," a prison in which all the cells can be observed from one point.
"The more worrying issue is its use of digital information consumption as a psychological control vector."
Other experts were sceptical that fears about personal information being used to influence users would lead to an exodus from the world's biggest social network.
But with hashtags like #DeleteFacebook and #ZuckSucks trending even on Facebook itself, they said it had suffered a major blow beyond the billions wiped off its share price.
Addicted to the 'F' key
French sociologist Nathalie Nadaud-Albertini said that with Cambridge Analytica a line had been crossed even if "people are almost inured to their data being used for commercial gain.
"That information is being used in political campaigns is far more unsettling," she said.
"Yet whether we like it or not, we are almost obliged to have social media accounts," she said.
Nor can addiction be underplayed, insisted Professor Eric Baumer, of Lehigh University in Pennsylvania, whose 2015 study for Cornell University showed how many Facebook users wanting to quit still found themselves reaching for the "F" key when started their computers.
Those who did leave were often tempted back, he said.
"A lot people are going to make a big fuss about quitting now... Then you'll see a negative backlash when their friends say, 'How am I to get in touch with you?'" he said.
No other social media "has the same critical mass. However, that could change" and there were strong signs it was already changing with younger users.
The most consistent users are now aged between 40 and 60, Baumer said, while "younger users are likely to have an account that is deactivated or to have at least thought of deactivating it.
He was now studying a growing "latent resistance" to Facebook, which may end up with a "more thoughtful engagement with a panoply of different types of social media.
"The other problem is the opacity of social media conglomerates," Baumer argued. "People say I don't like Facebook so I use Instagram... not realising Facebook also owns it."
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