My husband, who is an amazing and talented and handsome children's pastor (ok, I'm biased) wrote a little blurb on his blog about why parents are not their kids' friends. Or why they shouldn't be if they're trying to be. He said it very well, and I really don't need to comment, but you know, I like to talk. :)
I simply wanted to add that many times parents feel negatively about not being friends with their kids. They shouldn't. I am not my child's friend, I am her mom. It is not less than a friend relationship, it is more. Not being her friend doesn't mean I am not 'friendly' with her. We hang out, play games, tell secrets. But I get to add to those things the training, coaching, teaching and nurturing of a mother.
A friend's love has an end; a parent's does not. A friend tells us what we want to hear; a parent tells us truth. A parent is deeply committed to the spritual and character development of a child; his friends just want to have fun. The parent-child relationship should be so much deeper and more fulfilling than the friend relationship, even if it's hard sometimes.
So go out there and don't be your kid's friend. Someday they'll thank you.