How do you police your kids "virtual" life? Would you really get your teenage daughter a webcam?

I'm a stepfather and "dad" to a young lady who just finished her first year of high school. I've been her dad she since was 3, and she'll be 15 this summer.

She and her friends spend a lot of their time on myspace and youtube. Her mother and I monitor her, and when she strays we discipline her, usually by removing computer access. We were also blocking some of the social networking sites but realized that having her go to a friend's to live her online life could be much worse.

So now she's telling us that she wants a web cam.
We know that one of her friends has one, which they currently use to make "fun" youtube videos. But no chatting. so far.

I am adamantly opposed to it. My wife is mostly on my side, but seems to be weakening from the "I've got to be able to talk to my friends" whining. I feel like we're fighting a losing battle.

My biggest problem is that while there is always someone here to watch the kids (my wife is a teacher on the same schedule), this is not so at her friends houses. This particular friend has no father in the house, and is not thrilling us with her choices. We've had a few incidents in the last couple years. We also realize that when we say "no" here, our daughter often goes over there where she then does what she wants anyway, since mom is scarcely around and too busy to 'supervise.'

She has good grades and is a promising athlete.
We've told her that unless she impresses us that we can trust her "judgment" and conduct in these situations, she won't be getting her driving license anytime soon. I don't want to pull her from sports, since that keeps her busy, but I've also considered that.

I just feel like there's so little we can do.
I feel that while it's "okay" to have privacy, her virtual life allows her too much "secrecy." And that makes me uneasy.

I'd really welcome any suggestions from parents in dealing with a teenage daughter's "virtual life."