(pzler I love your avatar I love Mojojojo! the girl in my sig is a japanese model called Rena tanaka)
I think girls aren't reqlly intending to sleep with a guy at their young age, they just want the thrill of "conquest" I knew a girl who never lost this thrill, and even when she has boyfriends still feels the need to find out if she can "get" a guy.
Guys have healthy urges to have sex, and so when a girl is all over you with initially the intention to just "conquer" you, and all you have on your mind is sex, she's going to think that that is what it takes. now we all know that woman enjoy sex as much as men do. it feels good to them too. and when your young, you want "good things" as much as you can so I guess being exposed to sex at a young age, can make you promiscues. also media has definately lowered the bar. I lost my virginity at 14 and I remember that untill that moment, I thought that there was nothing more great and important then losing my virginity like all the guys in the teen movies. when I finally did lose my virginity, I remember thinking: so, that's it? that's all there is to it? there's nothing special about it at all!
another recolection I have, is when I was only 12 and a lady friend of my sister spend a night at our house. at one point she came to my room and like little kids we went: I'm in love with you blablabla. and I remember that she took her clothes off because in the movies, people that are in love take their clothes off. I know not every teen is that idiotic, but still I belive it's a nice example of media influence.