depends how you use it, its great for keeping in touch with family and friends that don't live so near,
friends who otherwise you might not share contact for long periods of time,
what you say post or photos, common sense is don't post anything you wish to keep private,
and just like you would in the flesh world, have respect for peoples feelings, you wouldnt say certain things if dont want to hurt or offend them, so why should it not be the same on facebook or any other online media