Stowe Boyd gets a little excited about Yahoo!'s MyWeb 2.0 and makes an interesting connection:
I continue to believe that the center of the social universe is the instant messaging buddy list metaphor: not just because I am biased toward real-time communication, but because human beings are the center of the socialized world.
The tie between social connections and buddy lists is great, the rest I think is a false dichotomy. I agree that tools for managing social boundaries, of which buddy lists are an important example, should be prominent in socially oriented apps. They're not the center of the world though, as the actual activity and media that connect people are what's really important. However, there's no reason a well designed app can't keep help users manage both aspects.
In most of these systems, there's "stuff" and "people". Both are important to end users.
But tools like buddy lists are sorely undervalued in many web applications. Witness the constant requests for private bookmarks in del.icio.us. Meanwhile, I admire Flickr's lightweight, but apparently effective, tools for managing social connections.