On July 21 this year, social networking site Facebook proudly welcomed its 500 millionth user to the online fold.

It’s a mind-boggling statistic, even more so when you consider that seven years ago, no-one had heard of the site. Indeed, it didn’t exist.

In less than a decade, an idea born in the hallowed corridors of Harvard University has quite literally taken over the world and changed the way we communicate.

As one of the characters in The Social Network, David Fincher’s expertly crafted film about the creation of the site, quips: “Bosnians – they don’t have roads but they have Facebook.”

Like all good ideas, the site has made its creators very wealthy but as Ben Mezrich’s book The Accidental Billionaires chronicled, the turbulent history of Facebook led to not just one but two lawsuits.

Working from a screenplay by Aaron Sorkin, Fincher employs a fractured chronology to dissect the jealousy and betrayal which underpinned the success of the site.

The Social Network opens by introducing central protagonist Mark Zuckerberg (Jesse Eisenberg), a computer nerd whose lack of social skills become apparent as he is deservedly dumped by his girlfriend (Rooney Mara).

In revenge, Mark spews bile in an online blog then creates a crude website called facemash.com, which racks up “22,000 hits in two hours” and brings the nerd to the attention of Divya Narendra (Max Minghella) and Winklevoss twins (Armie Hammer), who want Mark to program their internal social networking site called HarvardConnection.

Soon after, Mark approaches friends Eduardo Saverin (Andrew Garfield), Dustin Moskovitz (Joseph Mazzello) and Chris Hughes (Patrick Mapel) with an almost identical idea.

The whole campus excitedly logs on and the friends expand to Stanford and eventually across the Atlantic, before Sean Parker (Justin Timberlake), the entrepreneur behind Napster, becomes involved and offers Mark his advice.

“Drop the ‘The’. Just Facebook. It’s cleaner.”

The Social Network is technically flawless, powered by Fincher’s direction including a bravura rowing sequence at Henley Regatta set to a reworking of Grieg’s In The Hall Of The Mountain King.

Sorkin’s screenplay is equally polished – so much so that characters speak without hesitation or pause for thought, which strains credibility, even at one of America’s most revered seats of learning.

Eisenberg’s compelling, one-note performance fails to reveal any chinks of humanity beneath Zuckerberg’s thick skin.

Indeed, to the final frame, the character is an emotionally cold and unsympathetic loner, which leaves us with no-one to root for as the legal battle turns nasty.

Garfield is much more likeable and when he vows revenge against Mark, seething: “I’m not coming back for 30%, I’m coming back for everything,” it’s the closest we come to a rush of adrenaline.

STAR RATING: ***