I don't know what we'd do without FB now, because it allows our whole family, scattered everywhere, to stay in touch simultaneously. I have reconnected with lost cousins and furthered the family genealogy research. I have also "met" people all over the globe, and have visited a few of them in person during our travels. That was fabulous! I've been turned on to books I might have missed, movies I might not have seen, and music new to me. Finally, we don't watch TV, so a Friend's posting on FB is often the first news I hear of something. FB is like a kiosk: You don't have to stop and read everything stuck there, but it is available if you are curious.
Yes, you have to protect your privacy on FB, as anywhere else. I don't use my real surname, and many of my friends don't either, and we never enter any personal info like birthdates, home addresses, and the like. If someone wants to steal pictures of my cats . . . well, no skin off my nose.