Last year, billionaire Mark Zuckerberg set himself a challenge: travel to every US state he'd never visited. This year, he set himself a more daunting goal: to "fix" the platform that he engineered to build a community — but which is increasingly blamed for warping it.
Yet things continue to get worse. Scrutiny of Facebook has intensified following reports that it failed to prevent the data-mining firm Cambridge Analytica from amassing personal information about millions of users — possibly used to aid Donald Trump's campaign — and that the social network has been collecting Android users' phone call and text message histories without notice.
That adds to criticism that Facebook manipulates its users and has allowed Russians to divide Americans by spreading false information.
This week, the Federal Trade Commission announced it was investigating Facebook's privacy practices.
Throughout the mounting crisis, Zuckerberg's response has been a study in contradictions. He preaches transparency, but flinches at questioning and craves privacy. He is undeniably brilliant, but stubborn in his reluctance to acknowledge the extent of Facebook's problems.
Even his critics say he is uniquely capable of righting the ship. But at 33, is he prepared to do all it will take?
"If he fails to do it, it may take a while but eventually people are going to rebel," says Roger McNamee, an early Facebook investor and adviser who has become one of the company's most pointed critics.
"I thought Facebook was a force for good in the world for a really long time," McNamee says. "I think it's really hard to make that case today."
Days after Trump's election, Zuckerberg was asked about the possibility that foreign agents had used his social network to divide voters.
"The idea that fake news on Facebook ... influenced the election in any way, I think, is a pretty crazy idea," he told a California technology conference.
"I think all of us were shocked to learn how wrong he was," says David Kirkpatrick, the author of a 2010 book about Facebook who questioned Zuckerberg that day. "You can certainly say that he was culpable, in that he was naive and inattentive to what was happening in his system. But I don't think he was lying."
Zuckerberg's boyish appearance, even today, is a reminder of just how young he was when he created what would become the world's biggest social network, back in his dorm room at Harvard.
"I didn't know anything about building a company or global internet service," he wrote in January this year. "Over the years I've made almost every mistake you can imagine."
With Zuckerberg, "it's experiment, learn, experiment, learn," says LinkedIn co-founder Reid Hoffman, who has known him since 2004. But in the process of learning, Zuckerberg's inexperience has sometimes played out in public view.
I thought Facebook was a force for good in the world for a really long time. I think it's really hard to make that case today.
In 2010, Zuckerberg announced on Oprah Winfrey's television show that he would donate US$100 million to schools in Newark, New Jersey.
Critics labelled it an attempt to polish his image, just as the biopic The Social Network was being released. Still, there was little questioning his generosity. The problem was that Zuckerberg — who knew little about education — made the gift with few specifics outlining how it should be spent.
By the end of the process, Zuckerberg had developed a clearer understanding of how to get things done. He and his wife, Dr Priscilla Chan, have since chartered their own foundation and structured it to take on mammoth goals, like a US$3 billion investment to cure, prevent or manage all diseases. He has pledged to donate 99 per cent of his Facebook stock to philanthropy.
"Zuck's maturation has occurred in front of the public," says Kirkpatrick, author of the book The Facebook Effect. "But he also still lives with the consequences of the decisions he made when he was less mature."
At Facebook, Zuckerberg has grown increasingly bold in using huge sums of money to pursue corporate goals, which includes purchasing competitors — or companies that could grow into competitors.
Facebook's US$1b purchase of Instagram in 2012 — then unprofitable and little-known — came as a shock to Wall Street. Two years later came the multibillion-dollar deal to buy WhatsApp, a company that remains unprofitable but has given Facebook a prime portal into developing countries and other regions outside the US.
Last year, in a bid to free up his fortune for philanthropy, Zuckerberg pushed board members to restructure Facebook's stock, allowing him to sell off part of his stake while maintaining control. That prompted a suit by a group of shareholders who argued that the move would benefit only Zuckerberg while diluting the value of other investors' stakes. Days before Zuckerberg was scheduled to testify as part of the suit, the company dropped the plan.
The gambit hints at the complexity of being Zuckerberg, who advocates for transparency and the interests of the community, but whose individual interests don't always align.
The paradox is self-inflicted, the tradeoff for creating a venture based on users' willingness to share details of their lives. That requires Zuckerberg, who has 105 million Facebook "friends", to reveal far more about himself than would be expected of any other CEO, whether it's photos of him and Chan baking sweets for the Jewish holiday of Purim or dressing their daughters for the Chinese New Year.
I do not think [Zuckerberg] has yet grasped the gravity with which his service is being perceived to be a socially harmful force.
Yet he fiercely guards his privacy.
When calls went out last year for Zuckerberg to testify before a Senate committee, the company sent its lawyer. And when he and Chan bought 280 hectares on the Hawaiian island of Kauai last year, they quietly filed lawsuits against hundreds of Hawaiians — withdrawn after protests — that would have cut off locals' access to the land by negating their interest in small ancestral tracts.
"Intellectually, he believes in transparency," Kirkpatrick says. "But emotionally, it's very difficult for him."
Facebook works hard to present Zuckerberg as someone deeply interested in the ordinary people whose lives are at the heart of its business.
Stops on last year's US tour, never announced, were set up by facilitators who revealed details to only a select few. But many of the visits were covered by the media and documented in professional-quality photos on Zuckerberg's Facebook page soon after he'd departed.
As Zuckerberg connected with Americans face-to-face, controversy over Facebook continued to spiral.
Shortly before the election, McNamee sent a letter to Zuckerberg and Facebook's chief operating officer, Sheryl Sandberg, warning that Facebook was being manipulated in ways its creators never intended.
It wasn't just about the US election: a consulting firm had collected data on people interested in the Black Lives Matter movement and sold it to police departments, and critics had detected a well-organised, clandestine campaign supporting Brexit.
All this pointed to a deep problem with Facebook — that it was simply not equipped or not willing to prevent the misuse of its platform.
McNamee says he has been disappointed in the incremental changes announced since.
Facebook has adopted this "libertarian philosophy that says 'we are not responsible for anything downstream, we are allowed to disrupt media, we are allowed to addict our users and we are not responsible for any of the consequences of any of that'," he says.
Zuckerberg could change that. But McNamee says it is not enough to hire thousands of workers to weed through fake and abusive posts if those posts keep getting through. And tweaking Facebook's newsfeed so users see more posts from families and friends does not address his certainty that the algorithms underlying Facebook make it dangerously addictive.
"You cannot cure addiction by doing more of the thing that got you addicted in the first place, which is what Zuck recommends," says McNamee.
Critics say Facebook continues to ignore the possibility of the social network being used for dark purposes, but Zuckerberg's supporters counter that he is unfairly blamed for problems he could not have foreseen.
Hoffman, the LinkedIn co-founder, credits Zuckerberg with leading Facebook through a shift in mindset, making changes that will nudge users into a more positive virtual environment — without completely shutting out inflammatory content.
"Facebook basically is saying we enable people based on the way they behave," Hoffman says. "That's a very democratic argument. If people want to live in filter bubbles, who are we to say 'Don't live in filter bubbles', even though we don't want them to?"
But Kirkpatrick argues that Zuckerberg's and Sandberg's certainty that Facebook has a positive impact on society has blinded them to parallel realities. The company can't be fixed, Kirkpatrick says, until Zuckerberg comes to terms with existential threats to the way the social network does business — its potential to negatively affect democracy and the way it hooks in users.
"There's no question in my mind that Mark Zuckerberg is an ethical and responsible human being who wants to do the right thing," he says. "However, I do not think he has yet grasped the gravity with which his service is being perceived to be a socially harmful force all around the world. And I also don't think he realises the extent to which that really is true."
McNamee, recalling Zuckerberg as a 22-year-old visionary, says the CEO must be willing to rethink long-held assumptions. But that does not mean he has to abandon building his global community.
"You've won," McNamee says he would tell Zuckerberg if asked again for his counsel.
"You've achieved more than your wildest dreams. You're a billionaire. Now you have a chance to be a hero."