Stephen Downes

This is a really good and very visual way of representing the use of social network analysis to identify communities - or 'clusters' in networks. What the article makes really clear is that there is no one way to do this, and that different clustering algorithms will identify different numbers, and different types, of cluster. There is no one 'right' way to do this; it depends on which features you think are important, and what sort of application you have in mind.