I'm that mom who is my children's friend.
Why? Because being their friend means I take their needs - and their wants! - seriously; I listen to them when they speak; if they seem out of sorts, I help them figure out what's wrong rather than blaming their feelings on moodiness or selfishness; I ask for their help but don't have expectations that they'll give it; I don't interrupt them - or I look for an appropriate time to - when they're busy doing something important to them.
I am my children's friend because if they have an interest I don't quite jibe with, I don't tell them it's stupid or ban it from our home, I celebrate their happiness with it. If they're slow getting ready to go somewhere, I see what I can do to help, I don't stand at the door and yell. I happily prepare meals for them, even if they could prepare it themselves, because I know it says "love" to them when I do so.
I am my children's friend because I give them space to explore their own values, I don't expect them to share mine. I don't tell them what they should eat, and I don't say things like, "There's no way you could be hungry!"
I am my children's friend because I am their mom.
Blogpost inspired by this post. And this one. edited to add: There are many links to other entries in comments on both of those links!