Of social networks

Today, on the train from Portland and Seattle (I was in Portland for OSCON), I sat next to an elderly English lady (must have been in her mid-70's).  We spent a good chunk of the journey chatting.  Turns out that she was in the area to spend a couple of weeks with someone she has been pen friends with for 20+ years.  I've never had a pen friend, but I know others who have, and in a way, it's a somewhat slower, but a little more elegant way of having virtual friends, much the way we have today with Friendfeed, Twitter and the likes.  I have been lucky to have met a lot of my one time virtual buddies and have actually gotten to know some of them over time.

The question I can't help asking myself is, how can we scale these relationships.  Having a pen friend or two is easy to handle, but what about 300, or 5000 if you are Robert Scoble?  The next step in these tools, which have been more than useful for me, will be the ability to help users prioritize, and filter.