Meanwhile, MySpace's monthly traffic has been moving in a downward trajectory, with usage down 21 per cent compared with December 2007. In Britain, the BBC reports, Facebook has 17 million users or three times as many as MySpace. Globally, ComScore released figures late last month showing 222 million people visited Facebook in December, versus 125 million for MySpace.

Rupert Murdoch, chief executive of News Corp, which owns MySpace, will surely be eating his words now after last year dismissing Facebook as the "flavour of the month" and little more than a directory. MySpace spokesman Darain Faraz refused to comment on the figures. In a blog post marking Facebook's fifth birthday, founder Mark Zuckerberg, 24, said he was "humbled" that so many people were using the site to "engage and understand the world around them".

"The culture of the internet has also changed pretty dramatically over the past five years," he said. "Before, most people wouldn't consider sharing their real identities online. But Facebook has offered a safe and trusted environment for people to interact online, which has made millions of people comfortable expressing more about themselves."

To say thanks, Facebook, through its Gift Shop, is offering users a free "Thank You" gift card, which can be passed on to friends and appears on their profile page. Usually, members are able to buy gifts to place on their friends' profile pages including birthday cakes, drinks and flowers. Facebook also published a series of images showing the evolution of profile page designs from 2004 to today. It revealed that the average user had 120 friends on the site and more than 850 million photos were uploaded each month. Every day, 15 million users update their status to tell their friends what they are up to.

The challenge now for Facebook is to convert that momentum and its 150 million global active users into revenue. Last year, it generated only an estimated $US300 million in revenue, while MySpace, which has diversified into more of an entertainment site, was expected to book close to $US1 billion. MySpace has loaded the site up with ads while Facebook has taken a more cautious approach out of fear it might annoy users, who are suspicious of marketing messages being placed in between their communications with friends.

Facebook users in particular have been reluctant to accept new forms of highly lucrative, targeted advertising based on personal information provided to the site as this is seen as an invasion of privacy. Another problem with trying to earn money from social networks is that brands can advertise on the site for free by creating applications, starting up their own pages and running competitions. For instance, Burger King recently offered a free Whopper to people who deleted 10 friends in what it dubbed a "Whopper sacrifice" promotion, but Facebook did not earn a cent.