Why am I so private on sharing photographs of my ancestors?

-I have an Ancestry.com account with three family trees that are all private. I have many, many photographs of my ancestors on those private family trees. I really want to meet more relatives through ancestral websites and I heard about AncientFaces.com. I read the success stories and I'm currently making a decision of whether or not I should sign up. I like the idea of meeting more relatives but I have privacy concerns. Most of the photographs are of dead relatives. Please share benefits of making the photographs public. Also, I would love to hear of some free ancestral photograph sharing websites. Thanks!