I spent some time this evening playing with the TouchGraph LiveJournal browser.
I started off clicking on friends and friends thereof, following links and seeing what came up. Of course, the display bogs down when there are too many nodes on the screen, so I had to cull all nodes with fewer than N friends displayed repeatedly; I got up to 3 or more.
This is an approximation of journals around mine (of course, shaped by node-expanding choices). See the island in the north-east corner? That's Melbourne, or rather the Melbourne indie scene. London's in the southeast, the goths have the southern tableland, and the west and north-west appears to have a high concentration of geek types from the US West Coast.
When you switch in the showing of interests (which are drawn between those who share them), an interesting thing happens. Surprisingly, everyone there who's into Belle & Sebastian appears to be on Melbourne Coolsie Indie Chat Island.
I think, though, that one needs more than 2 dimensions for such exercises. How long, I wonder, until someone comes up with a graph-drawing library that works with OpenGL or somesuch, and a LiveJournal mapping toy that uses it.