I have a lot of people I like to talk to where I'm not close enough for 1:1 communication to make sense. Most of my FB usage is talking with these not-especially-close friends about whatever we're interested in.

Not that different from talking here, except that my FB friends (and especially my FB friends with FB's learned weighting of how interested I am in what each posts) are on average more likely to be interested in the same things I am and have more similar preferences around conversational norms.