Why on earth Facebook has not thought of this or done anything about it, I have no idea. But McAfee has an app coming right around the corner. You simply agree to the app that will initially be free, and here is what happens.
If someone goes onto your FB page to see your photos, all you will see is a blurry image unless you have been registered by the owner as a guest, AND they are using the software as well. Even then, if you try to right click or print screen, you get a big honking padlock and a message telling you that it's not going to happen.
Not totally sure how I feel about al of this as I see a few issue. First of all, who actually has my photos? Facebook, McAfee, or Intel? If it's free now, what will you charge later after you have my images hostage? What if I do want to show off a select set of images to the whole world? Is it an all or nothing deal?
I guess we will know more when the app launches in late August for PCs with MAC following along later. Until then, you can register to be notified when the service launches.