For a few months now my best friend (a girl) has been doing stupid 'naughty' things with this guy from school via webcam (he's an absolute jerk, one of the 'popular' people who wouldn't be caught dead even smiling at my friend) and now, all she ever talks about is either things they've sent achother or complaining that she's so horny she can't stand it! And she says she's aroused after simply giving her a friendly hug!
It's seriously starting to annoy the rest of us now, we've told her all this guy will do is use her and then drop her whenever he likes, and she knows that but all she says is "But he's so sexy! He's the only way to get rid of my sexual frustraition!"
Me and my friends are starting to think she needs to go get proffessional help, its all about arousal and how she wants sex 24/7 (she's a virgin s she can't be addicted to sex, surely?)
Is this normal for a 17 yearold girl? I mean, the rest of us don't go on like this at all! And she seems to have no shame whatsoever (a few weeks ago a picture meant for the Jerk accidentally found its way onto Facebook and everyone at school saw it and she wasn't the slightest embarrassed!)

What your friend doesn't understand is that this guy is more then likely recording everything they ( she) does. And its going to end up on the net and in front of everyone including her parents. Also if she is getting obsessed then yes she needs professional help. Since as you mentioned she is 17 its child porn. And after the Facebook "accident" ( yeah right ) arrests should have been made.

Perhaps she's the sort of person that only learns through (bad) experiences?

Not much you can do to control her so called horny urges I would suggest! By all means tell her she's stupid and he's a jerk, but in the end, hey, it's her decision.

Maybe you can suggest she gets a vibrator to satisfy her sexual urges? (safer and less embarrassing)

Well, she records everything he does in case he does something, believe me it would be far more embarrassing for HIM to say he's got pictures of her.
And the Facebook "accident" was because she accidentally sent a picture to another guy (who is an internet troll thing that has no life) who has the same name over msn and HE put it on the net.
Her parents were notified by the school and they simply took her laptop away for 2 weeks.
I didn't know it was child porn? Since you have to be 16 to do anything, we're in the same year as the other guy.
We've suggested everything to her and she says none of it will work without this guy seeing her! Its awful.

If this is happening in the U.S. then yes its child porn. And the 16 rule is a joke. Sure you can consent to some things but you cross many lines that are illegal. How old is this boy?

Ah well I'm in england.
He's 16 I think? I'm not entirely sure, we're all in lower sixth form (Equivalnt to the first year of college after high school)

Sorry your friend is going down a bad road, but its her choice and she will not listen until she gets hurt pretty bad.

The word for it is hardheaded, and that's something only she can change.

Well, she's already hit rock bottom. She's had the worst happen to her already and she hasn't changed at all. She hasn't learned from the bad. I'm thinking she's stuck for good now.