Problem is that a lot of people who are your ‘friends’ are people you don’t actually know.
Facebook has an application that maps all your friends, and which ones are mutual friends, amongst a couple other things.
I have just over 300 friends on myspace, and know them all personally. It seems like a big number, but between high school, college, rugby, and now, it’s not really that many.
One word: Tom.
So, two degrees, for virtually every user.
There’s also a facebook application called 6 degrees that is attempting to do just this…
I don’t even have a MySpace, and I know the first thing you do is take him off your friends list. Jeez. 
Well, if everyone has 50 unique friends, six degrees would produce about 15 billion friends. Of course not everyone is on MySpace. A relatively small number of my high school and college classmates are on MySpace or Facebook.
I was thinking about this the other day. Looking at my cricle of friends on facebook. There are three distinct groups, family, old school friends, and current work related friends. The groups are entirely separate from each other but have a lot of internal links. I thought, this six degrees of separation thing is crap, there’s not one thing linking these groups of people! 
I was wrong of course.
It’s not even clear that the “six degrees of separation” theory is correct:
The most that can be said is that some experiments seem to show that the average number of connections necessary between two random people in the world may be as small as six. It’s certainly not true that the maximum number of connections is six.