After a good long trial, I went through and deleted a bunch of "social" accounts. Found my time and attention taken, to no significant end. I tend to go through this exercise, regularly. Listen to lots of things for a while, then prune heavily.
Time to prune.
Twitter never really made sense. Too much idle chatter. Clearly some like the short-snippet format. Clearly some like a noisy, distraction-filled environment. Not me.
Google Buzz seems an improved variant of Twitter. Good for Google. Good for chatty folk. Not for me.
Getting rid of MySpace was a relief. Always found both the quality of construction, and the (unstated) premise ... revolting. Good riddance.
Friendster was never useful. There are likely a bunch of other tertiary "social" sites where I poked around, but found no use. Will kill when they bug me.
Facebook is the most recently-popular. Had an account there since it was mostly college kids. A year or so back, a bunch of folk I knew suddenly started showing up. Spent a lot of time there. Did not accomplish much.
Will keep Flickr (for sharing photos) - at least for now. Google Reader is immensely useful for tracking many things, and finding longer more thoughtful communications.