No matter how many cautionary tales abound, it's a truism that as long as humans have smartphones, some of those humans will use said smartphones to take photos of their naughty parts.
Snapchat, an ostensibly family-friendly app available now for iPhone, takes a slyly pragmatic approach to addressing this issue: if you can't kill the behavior, at least kill the evidence.
The app lets you send picture messages to your friends that will automatically disappear a few seconds after they've been read. While Snapchat doesn't explicitly require that those messages contain shots of your peen, the predominant use case for the service is pretty obvious.
Users can set their message to self-destruct anywhere from 1-10 seconds after it's been opened. If the recipient tries to take a screenshot of the image, Snapchat will ping the sender to let them know about it.
It's not quite a fool-proof system, but if you're gonna sext, at least use protection.