I see that Facebook has just signed up its half billionth user. Phew. But what's this saying, doing to friendship?

I suspect that the internet tends to exaggerate our virtues and vices. So it's easy to find examples of kindness online, and just as easy to find examples of abuse. Hence, it's both good and bad, and commentators tend to be either utopians or dystopians. But the truth is more subtle.

For example, Facebook must encourage the need for distractions - flitting from one thing to the next - and as we become what we are, it might be that deeper relationships, which take attention and time, might become harder to achieve. Related to that is the fact that the Facebook interface is pretty monodimensional, compared with all sorts of other ways you can interact online, let alone interact in real life: Facebook assumes you have one identity when, in reality, you have many that change according to who you're with. And Facebook arguably forces certain encounters that in the real world would be handled more humanely. This is the 'ignore' button phenomenon, when you're asked to be a friend, and have to say no. Causal callousness, you might say. You can also point to the fact that screens screen, so it can be unclear who you're interacting with.

But probably people get pretty smart pretty fast with this kind of technology. So, there's evidence that people use it both to stay in touch with close friends - to be virtually present to them - and to keep others at an appropriate distance, and not allow them to get too close. And remember the neologisms of Facebook - 'friending', 'defriending', 'unfriending'. They suggest users are aware that something different is going on compared with real world befriending, which is an altogether richer experience.

All in all, because of these ambivalences, I can't but help wonder whether Facebook will go the way it's come: our relationship with it is shallow, and as it's so speedily come to loom so large in people's lives, so it'll fade relatively suddenly too.