Friendship: The limits of social networks?

Christopher Allen says: “How do I maintain meaningful relationships with over 300 people?”
(So, Chris is thinking about his Dunbar number, the point at which the 300+ relationships on his social network sites don’t scale.)
This is a great question and Chris asks how others handle this issue.
Some thoughts:
I like the idea of keiretsu, the Japanese notion that a set of companies have interlocking business relationships and shareholdings–only I take it to mean a larger, loosely joined group of people with shared interests and compatible business objectives.
Beyond a circle of active friends are the keiretsu, the group with shared sympathies and interests–I use Linked In and Orkut to keep track (a little) of who might be within my larger network–friends, colleagues, and friends of friends with overlapping ideas or interests, but it’s really a pretty abstract list–I don’t try to make my social network lists comprehensive–so some good friends might not be there, will acquaintances are.
Dave Weinberger’s comment:”My own strategy is the same online as it is offline: Nod pleasantly and try to avoid getting yourself into a conversational corner where it becomes obvious that you don’t actually remember the person’s name.”