The latest crisis laying siege to the leading online social network has raised the spectre that he has lost control of his creation and been naive about the unintended consequences of people sharing so much about themselves.
"If Facebook was a typical company, and Zuckerberg was the founder, he would probably be gone," said tech industry analyst Rob Enderle of Enderle Group.
"He looks like a guy who really doesn't know what he is doing. He is not the hero that a lot of people had viewed him as; his reputation and image are badly damaged."
Facebook has prospered on digital advertising that benefits from being able to use what people share about themselves to target ads.
If Facebook was betting on people's better natures when it came to truthfully sharing, respecting others, and being able to connect with anyone, it wasn't always a winning wager.
The California-based social network has been a flashpoint for controversies about bullying, harassment, free speech, extremist propaganda, election meddling, privacy, and more.
"They don't put enough effort into making sure the user is protected and the experience is assured," analyst Enderle said.
"They only care about the advertisers, and the user is basically a digital slave."
Dropout to billionaire
A public apology by Zuckerberg failed to quell outrage over the hijacking of personal data from millions of people, as critics demanded that the social media giant go much further to protect user privacy.
Belatedly speaking out about the harvesting of Facebook user data by a British firm linked to President Donald Trump's 2016 election campaign, Zuckerberg admitted Wednesday to betraying the trust of its more than two billion users, and promised to "step up."
Vowing to stop data leaking to application makers and to give users more control over their information, he also said he was ready to testify before US lawmakers following - which a powerful congressional committee promptly asked him to do.
Zuckerberg has grown from a Harvard dropout who changed what it means to be social into a billionaire philanthropist bent on shaping a better world for his daughters.
Zuckerberg and his doctor wife, Priscilla Chan, have pledged to give away their Facebook fortune to make the world a healthier, happier place for children.
"Having kids changes a lot," Zuckerberg said this week in an interview with CNN.
"I used to think that the most important thing to me by far was having the greatest impact across the world as I can; now I just really care about building something my girls are going to grow up and be proud of me for."
Zuckerberg cemented his fortune, and a place in Silicon Valley history, by leading Facebook to a historic Wall Street debut in 2012.
The $16 billion (roughly Rs. 1.04 lakh crores) IPO was structured to keep control of Facebook in the hands of Zuckerberg, who has been Time's "Person of the Year" and cracked the Forbes list of 20 richest people in the world.
The hoodie-wearing 33-year-old, depicted in the Hollywood drama "The Social Network" as a socially challenged computer geek, has evolved into a confident chief executive.
Zuckerberg still favours t-shirts, jeans and sneakers, topped off by his trademark hooded sweatshirt and a mop of curly hair.
He is known for setting annual goals, which have included wearing ties every day; only eating meat of animals he kills himself, and learning to speak Chinese.
His personal goal this year is to fix Facebook, making sure it fosters real-world community.
Born on May 14, 1984, Zuckerberg was raised in Dobbs Ferry outside New York, one of four children of a dentist father and a psychiatrist mother.
He went to high school at the prestigious Phillips Exeter Academy, where he was captain of the fencing team, before entering elite Harvard University.
Zuckerberg launched Thefacebook.com, as it was then known, from his dorm room on February 4, 2004 with some of his roommates and classmates.
Facebook's early years were not without controversy, however.
In 2008, a $65 million settlement was reached with three Harvard classmates - twins Tyler and Cameron Winklevoss, and Divya Narendra - over their charges that Zuckerberg had stolen the idea for Facebook from them.
The conflict was at the heart of The Social Network, the Oscar-winning film written by Aaron Sorkin and directed by David Fincher.
Zuckerberg left Harvard in May 2004 for Silicon Valley, where he received his first major funding - $500,000 - from PayPal co-founder Peter Thiel.
He has been referred to by some as being struck in the mould of late Apple co-founder Steve Jobs. Zuckerberg has praised Jobs as a friend and a role model.