Andrew Leonard has written an excellent overview of social networking and "just what a friend is" in Salon.  It's a two part series.

Andrew kind of  took all my statements at face value, but it would have been nice to dive a little deeper into the various schemes being implemented right now and what'll be possible in the future - in so far as levels of relationship granularity.

Some folks just want a zero or one, take it or leave it approach to relationships - while others (like our PeopleAggregator project) support many levels of relationships.  No matter what, as long as we apply these social networks within particular contexts - like gaming, being Gay or within a virtual Silicon Valley - the granularity of relationships will come.

It's the only way to model real-life.