Sarah Sands: Zuckerberg is the master of a universe he has invented

For Mark Zuckerberg, the most irritating aspect of The Social Network was the way in which it cast him as a social reject and misogynist; a student who created his own online club, Facebook, because he was a failure with girls.

"They just can't wrap their head around the idea that someone might build something because they like building things," Zuckerberg said of the film-makers last week. Clearly, there is a cultural chasm between Zuckerberg's world and that of the despised film-makers. They are interested in the traditional ingredients of story telling: character, motive and plot. Zuckerberg is the master of a universe that he has invented. He and his 500 million friends write their own stories, just as they like. Facebook is a gigantic, awesome ego.

The numbers are so enormous, the business value so vast, that it is hard to have a perspective on Facebook. We know it is "cool", "massive" and has changed the way we think and behave, but what is it exactly? Part of the audience reaction to The Social Network is relief. We are back in familiar territory with a recognisably human intelligence, humour and scepticism.

Zuckerberg may not be faithfully represented in the film: in real life, he hung on to his girlfriend and he quoted Homer rather than making bitter and potty-mouthed observations about women. In other ways, he is more curious even than the film suggested. His lack of interest in money is the mark of a genius and also weird. If you are worth a billion, you can surely upgrade from a rented apartment with a mattress on the floor.

Zuckerberg says that Facebook was motivated by a vision of a new and open world. Yet the girl question is at the heart of his business model. I questioned a group of teenage boys who were among the earliest converts to Facebook. Did they feel the tectonic plates of their lives shifting?

Not really, they shrugged. It was just a useful method of tracking girls. If you met someone at a party, you could look her up afterwards and see if she was as fit as you remembered when you were drunk and it was dark, and if she was attached or could you have a crack at her.

We read a great deal about the nobler and warmer functions of Facebook; how grandparents are united with younger generations, how national prejudices are erased by global friendships. Then there are business offshoots that form career-shaping networks. But for the Facebook pioneers, it was all about girls at parties.

The excitement of a social life by other means lies in recognition. Among the thousands of recorded friends, only a hundred or so are of any interest. The other ground breaking asset of Facebook, according to my teenage focus group, was that the website was unusually clear and well designed. Mark Zuckerberg studied computer science at Harvard, and knew what he was doing.

People divide into two camps over Facebook and its impact. The first, the larger, responds with unconditional admiration. Zuckerberg is more revered than most world statesmen. He is a revolutionary, yet, paradoxically, he is very rich. The second camp is made of sniffy diehards who stress that they are far too busy – and by implication, that their lives are miles too interesting – to allow open access.

There is a third position, which is that we don't know, even now, where Facebook is heading. This has been Zuckerberg's claim and that of the film-makers. The Social Network is exactly the right response to Facebook. Zuckerberg is both brilliant and absurd. He is human, after all.