I'm actually not too sure about the conclusion drawn about LJ:
The blogosphere is the most explosive social network you’ll never see. Recent studies suggest that nearly 60 million blogs exist online, and about 175,000 more crop up daily (that’s about 2 every second). Even though the vast majority of blogs are either abandoned or isolated, many bloggers like to link to other Web sites. These links allow analysts to track trends in blogs and identify the most popular topics of data exchange. Social media expert Matthew Hurst recently collected link data for six weeks and produced this plot of the most active and interconnected parts of the blogosphere.
3 SHOW ME YOUR FRIENDS This isolated, close-knit online community of bloggers uses LiveJournal, an online host that primarily serves as a social networking site. This blogging island is just barely in touch with the rest of the blogworld.Of course I may just have a more outgoing reading list than many people here...
[Update: pulling out a useful comment by del_c that succinctly makes the point I was trying to make: "I bet that cluster is by definition the live journals that are linked to each other and not the blogs. I bet the live journals that are heavily linked to the blogs, and linked by them, are in the pack where they don't stand out like the cluster does. The existence of the cluster with a gap tells us that there is a difference between the two types of live journals, not that there is a difference between all live journals and all blogs."]