Interesting blog post by Cameron Marlow, research scientist at Facebook over at overstated.net: Maintained Relationships on Facebook.

They start from a simple question: is Facebook increasing the size of people’s personal networks?

They looked at the communications of a random sample of users over the course of 30 days and defined networks in 4 different ways:

• All Friends: the largest representation of a person’s network is the set of all people they have verified as friends. In research papers this number ranges between 300 and 3000. In facebook on average every users has 120 friends.
• Reciprocal Communication: as a measure of a sort of core network, we counted the number of people with whom a person had had reciprocal communications, or an active exchange of information between two parties. In research papers, this numbers ranges from 3 as individuals with whom I can discuss important matters (for Americans) to 10 or 20 as ongoing contacts at a university.
• One-way Communication: the total set of people with whom a person has communicated.
• Maintained Relationships: the set of people for whom a user had clicked on a News Feed story or visited their profile more than twice. This is a sort of over-the-shoulder relationship, I’m “following” (this is the relationship type) the target user without she necessarily knowing it. This is a new type of relationship (not really available says 50 years ago), similar to reading the flow of thoughts of someone via a blog or just looking at the pictures uploaded on Flickr.

An interesting observation: “as a function of the people a Facebook user actively communicate with, you are passively engaging with between 2 and 2.5 times more people in their network”.

And another one: The stark contrast between reciprocal and passive networks shows the effect of technologies such as News Feed. If these people were required to talk on the phone to each other, we might see something like the reciprocal network, where everyone is connected to a small number of individuals. Moving to an environment where everyone is passively engaged with each other, some event, such as a new baby or engagement can propagate very quickly through this highly connected network.