Here's an interesting diagram with regards to relationships at Bokardo:
The first is a diagram by Ben Schneiderman while the second is a diagram by Alex Mather. Both are trying to explain social networks and logic would dictate that the first should be true. In my personal experience, however, I'll probably follow the latter more than the former. But then again, Alex Mather's demographic is those ranging from 18-30 years and I'm still in my twenties.
Perhaps when I have a family of my own, my priorities will shift. It's also interesting to note how "people like us" quickly become assimilated into "friends" while it's probably more difficult for family and colleagues to "cross-over". And at the end of the day, one only needs to look at people's patterns in Livejournal, at who they filter and who they allow access to the "friends-locked" posts. Chances are, they're not just trying to block out strangers, but work associates and family.