Bono brushes off billionaire claim
The rock star's investment group Elevation put money into the social networking site, taking 2.3% of the company in late 2009.
But while the flotation means Elevation is worth way in excess of £1 billion, Bono is joined by nine other directors who stand to profit.
He said: "Contrary to reports, I'm not a billionaire or going to be richer than any Beatle - and not just in the sense of money, by the way, the Beatles are untouchable - those billionaire reports are a joke."
There had been suggestions that the canny investment could make his wealth outstrip that of Sir Paul McCartney, said to be valued at £665 million.
Yesterday's initial public offering (IPO) of Facebook shares on the Nasdaq Stock Market was one of the biggest ever US stock market flotations.
But despite the hype, shares in the company closed up just 23 cents on their first day of trading after being priced at 38 dollars each.
It made the site worth about 105 billion dollars - more than Amazon.com, McDonalds, Hewlett-Packard and Cisco.
By the end of the day, more than 500 million shares had changed hands.
Nick Einhorn, an analyst with IPO advisory firm Renaissance Capital, said: "It wasn't quite as exciting as it could have been but I don't think we should view it as a failure."
The IPO did not help the US markets, with the Europe debt crisis weighing on investors.
The Dow Jones lost 73 points, which means it has ended lower on 12 of the last 13 days, while the Standard & Poor's 500 and the Nasdaq were both down as well.
Mr Zuckerberg, who sold about 30 million shares, will retain a large stake in the company, making him worth an estimated 19.1 billion US dollars - the 23rd richest person in the world at the age of 28.
He said: "Right now this all seems like a big deal. Going public is an important milestone in our history.
"But here's the thing - our mission isn't to be a public company. Our mission is to make the world more open and connected."
One thousand millionaires were expected to be created by the flotation, including a small number of the 100 London-based staff and the sale of 421 million Facebook shares is thought to have netted up to 18.4 billion dollars (£11.6 billion) for the company.
James Hughes, chief market analyst at Alpari UK, said: "The real value of Facebook is not likely to be known until the hype of the IPO has died away and investors have been able to digest how the company is going to evolve to be the money making machine many expect it to be."
Before the IPO, many said they believed the stock was overvalued.
In a recent Bloomberg survey of 1,250 global investors, analysts and traders, 79% said Facebook's valuation was not justified and only 7% deemed the valuation fair.
Ajay Bhalla, professor of global innovation management at Cass Business School, said: "With its IPO priced in excess of 100 billion dollars, Facebook has no doubt been extremely successful in capturing the investor mood at the right time.
"However, investors cannot bank on the current undisputed position it commands in the social network world.
"The ability of Facebook to reinvent itself will depend not just on having a sticky customer base but also on its capacity to introduce new products."
And the company's laid-back management style that sees Zuckerberg wear his trademark hoodie and sandals may also have to change now the company is accountable to shareholders.
Facebook is the latest in a series of online firms to sell shares to the public in recent months, following online voucher firm Groupon in November and online games maker Zynga in December.