"In order to
compete in a crowded market of workers, the city-dweller had to continually increase a
narrow area of expertise. He also draws on Simmelís discussion of the move from
networks based upon family ties and local associations to those based on professions and
interests. Park claims that in the urban environment, every employment takes on the
appearances of a profession, and that those within the same profession tend to come
together."

from page 8 of this pdf document

This is fascinating...no really! A couple of friends and I were just talking about this over the weekend. Blogs are further defining and highlighting subcultures. It's quite an interesting phenom. The primary problem with a lot of blogs is that they are abandoned. I think if you're going to start a blog, you should commit to it, define your purpose, and embrace your audience.