So, what does “scale-free” mean anyway ? This article – Scale Free Networks offers up a good explanation.
In a nutshell, a scale-free network is a network where links between nodes aren’t added or distributed randomly. Iinstead of random attachment, you get preferential attachment – ie the more links a node already has, the greater the probability of a new node attaching to it.
Applied to the internet, you see this in super-connected sites such as Yahoo, Google, etc. In a social networking model, these hubs are generally known as “connectors”, and are normally responsible for bringing together disparate groups.