While I started blogging (in a sense) long before I had ever heard the word (back in 1997 or 1998, on MSNHomepages), my introduction to the modern world of blogging came via Howard Kurtz's column on the Washington Post. That led to me read Andrew Sullivan for a while, and to Daily Kos, where I really found a home for a while.
In essence, dKos was too big for my taste. Too many comments, too much buzz. It's a great place to read things, but it's difficult to get to know people unless you're there every day. So, while I continued to read the frontpagers, I stopped commenting and rarely read comments. Too noisy for my taste. Fast forward a couple years, and I found myself at ScienceBlogs. My first "home" was Pharyngula, but again, too many comments, too much noise. Nothing compared to a posting on dKos, but the signal to noise ratio is still too low for it to be worth reading 20 or 30 comments. Sure, I join the conversation from time to time. But it isn't the sort of community I am looking for. Now, I tend to comment most at less popular blogs - Greg Laden's, or Abbie's. But at those blogs there's a tendency for the pool of comments to be too limited.
I suppose the alternative is a distributed community - when you run into the same people at several blogs, and get to know them. That, and building a community at my own blog. How you do that, I'm not quite sure...maybe that's a question for Bora.