First it was "move fast and break things." Then it was "connecting the world" and "building a global community."
Mark Zuckerberg's ambitious vision for Facebook spawned one of the world's most powerful companies, but he now faces a moment of reckoning as it becomes clear the social network has been hijacked and manipulated for very different ends.
Snowballing revelations on the misuse of the Facebook platform to spread disinformation, and to harvest personal data in ways users had never imagined, risks undermining the very business model underpinning the social media giant.
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Zuckerberg took an idea hatched in his Harvard dormitory and created a network connecting more than two billion people, crushing competing social networks while imagining new ways to connect friends to each other -- and for marketers to reach users.
The rise of social media fuelled a wave of optimism about empowering ordinary people, notably following the Arab Spring uprisings starting in 2010.
"I had the feeling in 2011 that digital technologies were inherently democratic and would fuel democratic revolutions around the globe," said Dannagal Young, a University of Delaware professor who studies social media.
Young said these networks did indeed help propel the Arab Spring, as well as social movements like Black Lives Matter or #MeToo -- but that the public had failed to grasp their darker side.
"People use these platforms and do not understand the economic model," Young said. "They don't understand what is being commodified, as is everything they do and everything they share."
While social networks appear to empower individuals by doing away with "gatekeepers" -- such as the traditional mass media, or political authorities -- the selling of user data can have the opposite effect.
"If the business model is predicated on selling user data, it can seem as democratic as you want but it's serving a surveillance function that undermines democratic values," Young said.
Facebook's reputation has been tarnished ever since 2016, following disclosures of Russian-led efforts to influence the US election -- notably by spreading "fake news" and other forms of disinformation on social media.
But things got markedly worse following weekend revelations that data on 50 million users was culled by a British-based political firm working on Donald Trump's presidential campaign, prompting calls for investigations on both sides of the Atlantic.
Zuckerberg, who began touring the United States after the presidential election, sparking speculation he might run for top office, last year offered his vision of a "global community" as more people become disillusioned with troubled political institutions.
"The world feels anxious and divided, and Facebook has a lot of work to do," the 33-year-old wrote.
But first of all, Zuckerberg will need to focus on the more immediate mission he set himself earlier this year: to "fix" his embattled social network.
'Polluted by bad actors'
Roger Kay, a technology analyst and consultant for Endpoint Technologies Associates, noted that Facebook is just one of many online firms that make use of detailed digital records on its users' activities, which can rarely be expunged.
"Facebook adds to this, but it's not the cause of the problem," Kay said. "The problem is your long-term digital footprint."
Young, of the University of Delaware, voiced optimism that users can regain better control over their Facebook data -- as more people learn about online privacy and how to determine what is shared about them.
"We as users have a lot more control than we think," she said. "If enough users go in and change their settings, Facebook will be forced to respond. I do think there is a fix but it requires a whole lot of learning."
Then comes the issue of disinformation -- which Facebook has been under mounting pressure to combat.
Emily Vraga, a George Mason University professor of communication, said Facebook has taken positive steps in ferreting out false information in recent months.
"But I would like to see even more of that," she said.
One way, she said, would be making Facebook's algorithm available.
"I do think the public should be more aware" of how the network operates, she said.
For Young, both Facebook and Zuckerberg appear to have assumed that "when you crowdsource things the truth will come out" - a belief that appears naive in light of the "fake news" phenomenon.
"It could be that 98 percent of people on Facebook do it in good faith," she said, but "it doesn't take a lot to undermine that system."
Kay also voiced doubt over Facebook's ultimate ability to eliminate all malicious content without examining every item on its platform - an impossible task.
"They can't curate something with two billion users, there aren't enough editors out there," he said. "And if they held up the content, the users would go away."
He also notes that Facebook is not the first digital firm to be manipulated in such a way."Social networks have come and gone," Kay said. "They are first seen as an amazing way to connect people and then they become polluted by bad actors."