There's a theory of "Dunbar's Number"; from looking at the relationship between the size of social units in primates and a particular region of the brain, it's been extrapolated that there is a number (estimated to be about 150) that is hard-coded into our brains as the limit of how many people we can maintain stable, social relationships with.

Seth Godin talks about Dunbar's Number being a law;

Some people online are trying to flaunt Dunbar's number, to become connected and actual friends with tens of thousands of people at once. And guess what? It doesn't scale. You might be able to stretch to 200 or 400, but no, you can't effectively engage at a tribal level with a thousand people. You get the politician's glassy-eyed gaze or the celebrity's empty stare. And then the nature of the relationship is changed.

I can tell when this happens. I'm guessing you can too.

I don't think I completely agree with this point. The thing about "Dunbar's Number" is that it's not just about the number of people that one person can engage with effectively, but the total "unit" of people effectively engaging with one another. It's not just an important concept and the average happens to be "about 150"; it's an important number because it's an average.

So while I might only be able to "effectively engage" with a couple of dozen people, my friend might be able to maintain friendships with 300 people— knowing who they all are, what they are like, what is going on with their lives, what they like and dislike, who they are friends with and so on. In any given group there will be some people who are "better" connected with others, but the more people are in the group, the more important that average number becomes. Because it's not just about what I hear about my friend from my friend; it's also about what my friend tells me about our mutual friends.

The catch is that even though I might have 1,000 "friends" across your various social networks (school, university, work, sports, Facebook, Twitter etc. etc.), very few of those 1,000 friends will be connected to one another. Even though I might feel truly connected to one of my "Facebook friends", if they go through something massive in their lives that they don't want to share with Facebook then I might never find out about it. A huge chunk of their life is sitting in my blind spot, and because I can't see it, I don't even register that there's a blind spot there. (And if my friend doesn't want to share his recent break-up with Facebook, then it's probably less likely that our mutual Facebook friends are going to raise the subject either.)

"Celebrities" shine a light on where things might get really interesting though. Millions of us manage to keep track of the lives of Peter & Jordan, Stephen Fry, our favourite bands, the England football squad, manager and half of the Premiership (and the squads of the various rugby, cricket, or athletics teams), the cast of Eastenders, our favourite Hollywood directors, the most important politicians and so on and so forth— all on top of the 150 or so "proper" friends we are keeping track of— so there's clearly something more going on with the people we keep track of than just our "social units." But in the past, this kind of "relationship" has been a purely one-way; all we know about them is what we see or hear through the lens of the media. But now it might be what we see from reading their blogs, following them on Twitter, or being their fans on Facebook. So those "one way relationships" start overlapping with our "real" friends' relationships; like the people from school who we keep track of by following their Facebook updates but never seem to find the time to reach out to them beyond the occasional brief chat about their latest status update or a comment on their photos.

So when we've got hundreds of "friends", it's not that the "law" of Dunbar's Number is being violated; it's that our personal social networks are no longer working within it's domain. After all, we don't live in a single social unit of the kind that the primates Dunbar was studying lived in— but maybe the way we connect with one another is making those "loose" social networks more important.

Probably not as important than our "tight" networks- but considerably more important than they used to be. Because it's not just about "friends", but anyone or anything who you might be interested in; whether that's your favourite actor, writer, comedian, or maybe even your favourite brands…