+1
Also, I seem to have a lot of friends who treat Facebook the same as Twitter (or at least as far as I understand Twitter, since I'm not on Twitter). They'll post Status updates, and I'll comment sometimes, ask questions sometimes, you know, actually try to get a conversation started. They never follow up. They just threw stuff out there.
One time this guitarist I know posted " and <another guitarist I know> learned to play stick today!" I commented "The Chapman Stick? That's a cool instrument." Nothing. I wanted to talk a little about Sticks. Facebook is often like a message board of all people you've actually met in real life. I figure if you bring something up, you wanted to talk about it.
Then there's a people who post stuff like " is totally bummed." But even if 10 people ask what's wrong, or offer sympathy, they don't reply. They just wanted you to know they're bummed. About something, apparently.