Dottie, I think it's a forum-level setting.
I see both the Tweet and FB buttons at the moment, but the FB one appeared a long time after the rest of the page finished loading. They are on every thread.
I personally wouldn't "like" a conversation here, in large part because I don't want people who know me from elsewhere, and who aren't active participants here, to necessarily follow me to here. (Which is also why I use a completely different username here than the "standard" one I use pretty much everywhere online.) There's no anonymity on the internet, but that doesn't mean I have to make it easy.
