When I was growing up, my friends didn't understand why my parents were so open about the things they let me do. And it was simply because they trusted me because I didn't give them any reason not to. I'm not saying I never got in trouble, but really, that one time the principal had to call my dad... I'd already called him 10 mins before to tell him the principal would be calling.
But yeah, I hope if I ever have kids, we can have a pretty open relationship and they feel like they can actually ask me about things instead of sneaking around behing my back.
But since I don't have even have kids of my own, I'll quit preaching on the subject.