I don't think it's so much the fact that sex is shown that's the problem, as much as it's how it's shown. Sex shouldn't be marketed to kids in such a manner. They give kids the wrong idea about nudity, and will probalby cause them to want to follow the example
An entirely on-topic reply! To which I cannot but agree. I'm pretty far from a Puritan, but I think some things should always remain a no-no (cf. my initial post).
Kids, at early age, are conformist by nature, and will want to try everything. This is only natural. But society should realise that it's not just parents having an 'educational' responsible task towards children. It's the media as a whole.
In these times of mass communication it's very easy for, well, anyone to be exposed to anything, so it's already quite hard to keep children "from harm's way". So as far from all dangers can be avoided, I think it's important that kids are taught not only about sex, but about the media and let them see how society works - especially the part where it's obvious that society tries to manipulate children. This has long been the case for things like games, toys, movies and certain hypes in general, but has completely extended to things like make-up, clothes, music, and so on. Children are vulnerable, and will get influenced. So it's important to create awareness, too.