OK, so why are we hating on the guy (or girl) who distributed the picture to the Internet?
If someone is given something, they've presumably been given privilege to do with it as they please: masturbate to it, respond to it, share it with friends, share it with the world. Whatever, as long as they don't sell it. That's how these things work.
Don't like it, and don't trust the other person as much as you do a close friend or relative? Sign a contract - presumably goods of some sort are being exchanged, yes? Maybe it's nude pictures for esteem, perhaps.
Or, better yet, follow the following protocol: don't be a slut, or at least be a bit more selective. That goes for guys, too, though obviously there are more women sending nude selfies than guys. If you're going to trust someone, be damn sure they're trustworthy. (You have sex with a condom even when you trust someone enough to let them smear their genitals all over your own, so why not a little precaution with pictures?)
There's so much porn on the Internet at this point that I don't really get the fear. There are so many unnamed boobs on the Internet at this point (not including ACs) it hardly matters.