Darren at Problogger suggests that we could meaningfully consider the inter-relationships between blogs as a series of topical spheres within the larger sphere. This is both interesting & useful. I would like to suggest that blogs can also have multiple identities. A blog might be very strong on a single topic that only a few folks are interested in, & therefore be a big blog in a small sphere, whilst also commenting less definitively on bigger issues, & taking a peripheral place in a larger sphere.
There's a social aspect to this too. Regular readers, commenters and subscribers here form a sphere of sorts that has very little to do with any "top 500" action, but has a great deal to do with how this site develops from day-to-day. Those readers also contribute to other spheres, many of which I am not a part of. That sense of multiple developing communities is one of the things that I find so involving (addictive?) about this process.