Usual rules do not apply when your company will float on the stock exchange for the first time this Friday with a valuation of £62billion.
Wandering into the great financial houses of Wall Street in a hoodie this week, it’s a wonder Mark Zuckerberg wasn’t thrown out by security.
Pin-striped suits and expensive tailored shirts are the usual uniform here.
And when curly-haired Facebook founder Zuckerberg turned up to promote the social network site’s shares flotation in a black-hooded top, jeans and trainers, billionaire investors looked on in astonishment.
Wall Street just about got used to the finance whizzkids of the 1980s wearing red braces yet nothing could have prepared them for this.
But usual rules do not apply when you’re one of the world’s youngest chief executives, whose company will float on the stock exchange for the first time this Friday with a valuation of £62billion.
That makes it worth more than McDonald’s or Goldman Sachs, although investors still weren’t impressed with how he dressed.
One top stockmarket analyst said: “I think that’s a mark of immaturity.”
Zuckerberg, who turned 28 on Monday, was also voted one of the world’s worst-dressed men by magazine GQ.
But there is method in his fashion madness – his trademark hoodie is in fact a piece of Facebook merchandise and displays in grey the three logos for “friend requests”, “messages” and “notifications”.
It’s not just his dress sense which is seen as slightly out of the ordinary, though.
He carries two business cards, one simply stating his lofty position as company “CEO” but another, for less formal occasions, which reads “I’m CEO…b*tch!”
At work at Facebook HQ in Menlo Park, California, Zuckerberg has no office and instead holds court among accountants, engineers and internet gurus at a messy desk in the middle of the huge room.
But he also rubs shoulders with America’s rich and famous, including President Obama, pop star Katy Perry and rapper Snoop Dogg.
And on one wacky day, a grey-haired man burst into the HQ surrounded by an entourage.
He was the oldest in the room by 20 years and the only one wearing a suit.
Marching up to Zuckerberg he introduced himself as Robert Mueller, director of the FBI.
They shook hands and chatted about nothing for a couple of minutes and then Mueller promptly left.
One worker said: “There was a giddy silence while everybody just looked at one another as if to say, ‘What the hell just happened?’”
Welcome to the weird and wonderful world of internet entrepreneur Zuckerberg, who has almost single-handedly destroyed the productivity of workplaces around the world.
Yet he has a powerful work ethic.
When Facebook was in its early days, he and his co-founders and their small team worked relentlessly on the new project.
One employee remembers him refusing to let others out for a bite to eat, crying: “‘No! We’re in lockdown! No one leaves until we’re done with this thing.”
But when the tight group partied, they did it hard.
A zip wire was even fixed from a chimney to the ground so partygoers could drop into the pool from above.
And the landlord had to send a letter of complaint asking him not to throw furniture into the pool or walk on the roof.
Annoyed at the treatment of a pal by a venture capital firm looking to invest in Facebook, Zuckerberg turned up at a meeting in his pyjamas, with a PowerPoint computer presentation listing the top 10 reasons they shouldn’t invest.
He is devoted to his Chinese-American girlfriend Priscilla Chan and in 2011 spent Christmas with her riding a buffalo in Vietnam.
It is one of the few country’s in the world to block his social network site – and he then posted pictures of it on his own Facebook page.
The couple have been dating since their college days at Harvard, after meeting at a party while waiting in a toilet queue. Priscilla later said she thought
Zuckerberg was “this nerdy guy who was just a little bit out there”.
But despite all his bizarre quirks and oddities, he is already worth a staggering £10billion.
And he is in charge of a company which has connected 900 million people – almost one seventh of the Earth’s population – through a simple idea conceived in a dormitory of Harvard University.
But it was only last May he treated himself to a £7million five-bedroom house in Palo Alto, California, a handy 10- minute commute to the office.
Until then, despite his enormous wealth, the computer genius had been living in a relatively modest two-storey house on a street neighbours described as “absolutely average”.
No Ferrari, Porsche or Bugatti Veyron for him. Instead he went for a basic Nissan Infiniti, and nicknamed it The Warthog.
Tyler Winklevoss, one half of the Harvard and Oxford rowing twins who successfully sued Zuckerberg for millions claiming he stole the idea for Facebook from them, once said: “He’s the poorest rich person I’ve ever seen in my life.”
Each year, though, he sets himself a new challenge.
Bizarre as it may seem, given the way he turned up on Wall Street this week, in 2009 he decided to wear a tie for a year.
For 2010, he announced he’d be learning Chinese. “Some members of my girlfriend’s family only speak Chinese and I wanted to be able to talk to them,” he said.
“I blocked out an hour every day to study and it has been an amazing experience so far.”
In January, 2011, he wrote on his own Facebook page “Became a vegetarian”, writing that he only want to, “eat meat if I kill the animal myself.
“The reason for this is that I feel lucky for having such a great life”.
Zuckerberg, who owns a dog called Beast, wanted to feel more “connected” to the food he eats and the “animals that give their lives so I can eat them”.
The statement was “liked” by 25,168 of his 13 million Facebook page followers, and every wall post he writes gets around 300 comments.
The famously frugal tycoon has since killed chickens, a pig and a goat as part of his personal crusade for more responsible eating.
He said his first kill was a lobster, which he had to throw into a pot of boiling water.
Now he is telling friends he is interested in trying hunting.
A chef who showed Zuckerberg how to kill animals in the most humane way said: “He cut the throat of the goat with a knife, which is the most kind way to do it.”
Having slaughtered the animals, they are sent to a butcher, who then cuts them into parts and returns them to Zuckerberg and Priscilla to cook and eat.
For one recent meal, he reportedly ate a chicken, including the heart and liver, and used the feet to make a stock.
A photo of the chicken and the dishes he made from it were put on Facebook.
But for all his eccentricity, he’s definitely a trend setter.
In his honour, Australian fashion firm Betabrand has just released an “executive pinstripe hoodie” nicknamed The Zuck.