I almost never use LJ like a diary or journal, but as "public communication space."

Yes, this is pretty much what I do as well. I'm always a bit puzzled when people post "notes to myself" type posts. (Especially since you could just make those private and see them yourself just as well.) But as I said to Te above, I do think a certain amount of personal info can help with building relationships. I sometimes think I don't post *enough* cat stuff.