Wow, have you guys brought up a subject that really hits home. First off, madonna, I am very sorry about your cousin. He did the right thing and it was unfortunate that that his friend didn't recognize his limitations.
As a parent of two drivers and one soon to be, this is something I deal with constantly. When my son and I went to ballgames and tailgated, I'd share a beer with him, because I was always of the mind that if you taught your kids to do things responsibly, instead of denying what you know they're going to do anyway, they'd be better for it. I know he drinks in college. We've talked about it and he's honest with me. But, there is always that little thought in the back of my mind of whether or not he really knows what his limits are. Just last weekend, he came home for the holidays and went out Saturday night with some friends. He came home the next morning because he slept it off on a friends couch. While I'm glad he did that, he doesn't understand why his not calling us to just let us know that he won't be home causes us undo anxiety. Kids think it's a matter of control, when it's not. It's really a matter of concern and peace of mind.
Now my youngest is half a year away from her permit and she's already counting down the days. I'd like to say I trust my kids. I do. But how much are we willing to let go when just one mistake can prove so costly? I'm not that old that I don't remeber when I was 16. I thought I knew better too and in most cases, I did. I learned my lesson thankfully before I could do anything really stupid, but in retrospect that lesson could have been a costly one, instead of being something to look back upon and laugh at.
Bottom line is there is a fine balance between being a good parent and letting your children grow into independent young adults and being responsible enough to make sure they do the right things. I'm not sure there are any correct answers. You just have to pray that you've done your job well.