Facebook is a blight on humankind.
It's a great way for me to relate to my teenaged daughter, to interact with some of her GLFs (Grubby Little Friends), to see what she's into, what she finds funny and to share fun stuff (or political stuff). We do private chats together all the time.
I don't post anything on my own page, but I participate in her page all the time.
She and I are very close, although she doesn't live with me because her mom and I have been (amicably and cooeratively) separated for years. But I live close by, and see her often, drive her places, take her to dinner, help her with homework, giver her music lessons, etc.
But Facebook is a whole separate way to interact with her, and I'm glad it exists.
People who post personal info on facebook and other such sites are idiots.