However, look into academic literature on “weak ties” in social networks. There is an argument that, despite the weakness of a tie, it’s still valuable to maintain it, even nominally, even if you don’t talk on a “regular basis.”

They did a study of social behavior during the Hurricane Andrew disaster in Florida, and researchers discovered that while communication with “strong ties” increased somewhat (you called your mom to say you’re ok), the big difference in coping with disaster was the activation of these so-called “weak ties.” Even more so than simple strangers helping strangers, these “low frequency”, “just on facebook” friends become very useful.

Your reticent neighbor gets chatty when the neighborhood is destroyed, because extreme circumstances mean that the strong ties may not be enough. People that you haven’t talked to in years check in on you, and offer moral and practical support.

I’m pretty sure these observations bore out during the September 11th attacks too.

So yes, it’s good to maintain quality control over your definition of “friend.” But to prune all of your weak ties would be a loss (not that I think you want to). Loss, disaster, extreme circumstances simply shift your network need. Facebook tries to nag users to define these ties, but I can’t be bothered to add the information. I think in the long run, our computers and robots will be able to infer who’s actually a Friend and who’s just a weak tie.

Deleting people your AIM lsit is even harder. It’s like “I don’t even really talk to this person anymore but I don’t want to delete them neither…”