It's your body. You have a right to expose any part of it that you wish however you wish. But then WHAT IF?

I would never.  It is so dumb to me to ever expose anything that can hurt you.  I mean why?  What possible jewel do you receive from doing something like ruining your future?  It's like getting a tattoo on your face.  WHY?  

It announces to the Universe that you are stupid, thoughtless and cannot make decisions that may affect your future, your career and the lives of those who have to admit they know you.

So, the idea of showing your private parts is not what shocks me.  What shocks me is HOW STUPID YOU HAVE TO BE TO DO THIS.  

In this country, we have the "right" to do just about anything.  However, just because one has the "right" to do something won't negate any consequences of doing it.

One has the RIGHT to take nude photos of myself. One has the RIGHT to post said photos on the internet (freedom of speech?).  However, doing so may not be very prudent.   By posting those photos one is literally putting them into "public domain".  This means that anyone could see your "stuff", not just the one one intended.  What's posted doesn't simply "disappear" in a few hours.  No, it's there permanently.  Anything posted could very well come back to "haunt" one at a later date.  The nude photos one took of themselves when they were 19 may still be on porn sites when they're 50.  Think before you post!

I don't wish to seem as though I am going on the attack, but I do want to mention that you're question is worded in such a way as to appear both sexist and hetero-centric.  The internet is riddled with plenty of men who also choose to appear nude in various types of professional and home-made works.  As a matter of fact most men are more quickly willing to disrobe and show their "junk" than many women are.  This is especially true in Gay erotic/adult entertainment as well as the much of the gay community at large which is constantly throwing off the shackles of sexual repression by the hands of others.  I myself am a gay male who has worked as both a stripper and a performer in adult movies.  So the question of "what-if" where future family is concerned is a recurring issue for me along with other men and women, both straight and gay.  I have had many opportunities to reflect on all the different scenarios that could unfold if anything I did in the past (porn or otherwise) ever made its way to any young eyes in my care.  I have wrestled with how i might hide this information from them or whether or not I even should hide it, but instead be honest.  Its very difficult to say which I would do.  I would hope that i could protect my "sons" as you said, or even my daughters from pornographic material in their tender youth.  If they are finding my work online then the real problem might be my having a far too lax approach to parental supervision.  The internet being what it is though, pervasive and quite often uncensored I would surmise that anything is possible.  And as you made mention of, friends love to share things they've seen, heard, and done, with other friends.  I know I did the same growing up.  So many of the things in our youth however,  are just rites-of-passage.  And though many women wince at the very thought, porn for boys is just one more step on the way to becoming a man.  You don't have to like it.  You don't have to agree.  It is just my opinion, but the truth is the facts bear this out.  In other countries throughout Europe many of these ridiculously Victorian notions of sexuality have long since been done away with.  Things of this nature are not cause for shame nor do they determine their moral turpitude.  Americans still tend to be far more prudish, even frightened by the idea of sexual freedoms. Though the times they are a changing.  As it is, most all of us live in the moment.  Truthfully we have no guarantee of even our next breath. Its difficult enough to navigate the daily ins and outs of our lives without piling on the excessive burden of all the things which may or may not happen in the years to come.  There's a very well known remark which says..."we'll cross that bridge when we get there."  The way I see it, even children especially teens, without meaning to or even realizing it can do things during their growing-up that at times can mortify us, embarrass us, or even place a family in danger.  So there is often no shortage of questionable behavior on both ends of the age spectrum.  I have made my decisions both good and bad along the way and for the most part have erred on the side of "first, do no harm."  What I do with my own body, most notably things of a sexual nature, are not anyone else's place to judge in the public arena, and neither is it up for debate at home.   At the end of the day, adult entertainment is not illegal, and it can even provide a lucrative living.  Sometimes kids just have to realize, no matter how hard that is to do, that their parents had a life before them and will also have one again after they move on.  Besides, I have to give them something to talk to their future "shrink" about.