It's not that important, I just decided to sort them by size in the app that I'm developing. What I'm calling a ring is also a clique in graph theory terms, and since there are thousands of cliques in the social graph for a typical user, most of them aren't very interesting. I think it is interesting to see the largest rings a user is in, and many of the smallest ones are interesting as well because they highlight an unlikely interaction that occurred between a small group of people.