Aristotle distinguished between friendships based on communal interests and those of soulmates who bonded out of mutual affection. The vast majority of people signed up for MySpace, Rupert Murdoch's phenomenally successful networking site, fall into the former category. But on present showing that won't stop its continuing expansion which, as the MySpace generation goes into employment, could eventually extend Murdoch's influence in ways that would make his grip on satellite television seem parochial.

It was said at the time of purchase that if Murdoch tried to mess with MySpace's "sharing" culture by commercialising it, punters would simply switch to one of the dozens of clones it has spawned from Bebo.com to the upwardly mobile Cyworld.com, which has taken South Korea by storm and is now taking the battle into MySpace's backyard in the US. Cyworld points to research showing that MySpace is a "rites-of-passage" site that kids will grow out of while Cyworld is a "real you" experience. It is an interesting, almost Aristotelian, distinction but some argue it may already be too late for competitors to dislodge MySpace, except in niche markets.

John Barrett of TechNewsWorld claims that MySpace is well on the way to becoming what economists call a "natural monopoly". Users have invested so much social capital in putting up data about themselves it is not worth their changing sites, especially since every new user that MySpace attracts adds to its value as a network of interacting people.

It is common knowledge that a fax machine is worthless until others have one too. That is what is happening in social networking except that, unlike a fax machine, it can't be instantly swapped for another. It is easy to change search engines, even if it is Google. But if you change social networks you not only have to move all your videos, audios, messages, photos elsewhere but you also lose your network of friends unless they migrate with you. MySpace won't make that easy. Its massive user base will help maintain its dominance, according to co-founder Chris DeWolfe. "In social networking, there is a huge advantage to have scale. You can find almost anyone on MySpace and the more time that has been invested in the site, the more locked in people are".

If it were a country, MySpace would be the seventh biggest, ahead of Russia and Bangladesh, though not all users are active. It had 153,339,321 users when I started writing this article and 153,523,640 when I had finished. What does this growth bode for the future? For the first time a like-minded media generation will grow up interacting instantaneously: globalisation personified. Maybe we won't need CVs any more as our lives will be there online.

But will commercialisation kill the culture that spawned MySpace? The $900m (£450m) three-year deal Google did to put its adverts on MySpace is, reportedly, being renegotiated. Upwards. When I visited the site this week I was met by offputting flashing adverts. Logging on I was then greeted with a loud video advert there was no obvious way of turning off. Good job I was not in a library.

That doesn't bother MySpacers and they don't seem bothered by other matters. User-generated content, for instance. MySpace is a huge generator of it, maybe the biggest, but users don't get paid. But why not? Google, the owner of YouTube, the vast site that hosts video clips, is under siege from corporations, doubtless including Murdoch's Fox empire, to get royalty income from those clips. Yet MySpace creams off all the advertising income associated with user content without which MySpace's goldmine would vaporise. The difference is that YouTube's predators are large corporations, whereas consumer power is diffused among over 150m individuals on MySpace. Maybe they should form a virtual trade union.

· vic.keegan@theguardian.com

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