I have worked with youth for 18 years and I have told them on many occasions that they should not consider their parents to be their friends. I have also discussed this with parents of this youth and said the same. There needs to be a clearly defined parental position so that the authority it brings can be taught and enforced.
Does that mean that you shouldn't be "friendly" with your kids? NO! You should love up on them, spend time with them, talk with them, be interested in what they are interested in... but the roles need to be defined.