When I first heard about "sexting" I thought it was fairly benign: teens having explicit conversations of a sexual nature via cellphone texting (you know, "txt", the ubiquitious method of cellphone-to-cellphone communication to which every teen I know is completely addicted). Were that all it was.

In fact, sexting refers to when someone sends a sexually-oriented photograph of themselves via the cellphone, typically through something called MMS, the multimedia messaging service. Most commonly? A teen girl sending a provocative photo to their boyfriend.

Still, other than a bit of bad judgment, what's the problem?

The problem is that some of the recipients of these racy pictures forward them along to friends or even post them to online discussion and social media sites.

Now you can easily imagine the problem.

Marissa Miller, a 15yo girl in the sleepy town of Tunkhannock, Pennsylvania sure does. She sent a nude photo of herself to her boyfriend without thinking too much about the implications. Worse, she wasn't alone in this practice, other girls at Tunkhannock High School did the same.

It all exploded when a girl at Tunkhannock High noticed a boy scrolling through the photos on his cellphone and spotted a nude photo of herself. Now the law's involved, the local District Attorney is threatening to charge everyone involved with child pornography and Marissa and the ACLU are teaming up to sue him.

All because of a nude photo. That's what sexting is, and it really is an alarming problem and a very serious example of the law of unintended consequences: when cellphone manufacturers made it easy to both take photos and email them to your friends, they never imagined that this sort of thing could result.

In some sense, though, sexting is just an example of a greater problem, which is that people who are just joining the various computer and social networks don't yet grasp that nothing is ephemeral. Not your tweets, not photos that you upload to Flickr and delete the next day, not blog entries, and not reviews of wild parties posted to Facebook.

That's a message that needs to be communicated and it's not just about cellphones or sexting, but about the boundaries of smart and acceptable behavior. It's fun to share pics with your friends and to send suggestive messages to someone with whom you're in a relationship, but it's really dumb to cross that line and forget that whatever you send them can easily make it out to the greater online world, sometimes at your expense.

And as a parent? It's our job to make sure our children understand this, even if it's as blunt as their ability to have a cellphone and computer is the agreement that you can occasionally surf their photos and other written material to ensure that they're exhibiting good judgment and won't regret their rash youthful decisions when they're older. Don't forget to also highlight that it's also illegal to transmit nude or sexually suggestive pictures of children.

A good resource to learn more prevention tips: connectsafely.org