SOCIAL networking giant Facebook has filed its long-awaited plans for a stock market flotation.

The documents filed yesterday show the social networking site hopes to raise $5 billion (£3.2bn) in its initial public offering (IPO). That would be the most for an internet IPO since Google and its early backers raised $1.9bn in 2004.

The final amount is likely to change during the next three to four months as Facebook's bankers gauge investor demand.

The IPO marks another major milestone for a Harvard-born start-up that began as an online college hangout eight years ago.

Since then, it has become a cultural touchstone that has transformed the way many people share information about their lives.

Joining corporate America's elite would give Facebook newfound financial clout as it tries to expand its audience.

Founder and chief executive Mark Zuckerberg, 27, has emerged as the latest in a lineage of Silicon Valley prodigies who are hailed for pushing the world in new directions and reviled for overstepping their bounds.

In Mr Zuckerberg's case, a lawsuit alleging he stole the idea from some Harvard classmates became the background for a book and a film that was nominated for an Academy Award last year.

Even before the IPO was filed, Forbes magazine estimated his wealth at $17.5bn in its most recent survey of the richest people in the US.

Depending on how long regulators take to review Facebook's IPO documents, the company could be making its stock market debut around the time Mr Zuckerberg celebrates his next birthday in May.

The IPO filing casts a spotlight on some of Facebook's inner workings for the first time. Among other things, the documents reveal the amount of Facebook's revenue, its major shareholders, its growth opportunities and its concerns about its biggest competitive threats.

What is not in there, yet, is Facebook's market value. That figure could hit $100bn, based on Facebook's rapid growth and the appraisals that steered investors who bought stakes while the company was still private.

Mr Zuckerberg has made it clear he is not especially keen on leading a public company. He has said many times he prefers to focus on developing Facebook's products and growing the site's user base, rather than trying to hit quarterly earnings targets in an effort to keep investors happy.

However, he has matured into the role, said Scott Kessler, a Standard & Poor's equity analyst who follows internet stocks. "Clearly he is a very smart and shrewd person," he said.