I saw this article over on the Today Show page and thought it was interesting. Have you ever become friends on Facebook with the teacher of one of your children? Do you think that is a line that shouldn't be crossed or is it fine to become FB friends?
I'm FB friends with a few of my boys' old teachers, but not their current teachers (and we only became FB friends because we've become friends in real life). I can see how it would be best to keep that relationship more professional while the teacher/student relationship exists. However, if you are active at the school and get to know a teacher on a personal level, I see no problem with the teacher/parent FB friendship.