Should Teachers Be Allowed To Be Facebook Friends with Students?

I have a friend who is a teacher and they were recently talking about school policies and restrictions regarding students and social media.

She says that students will sometimes 'friend' a teacher on Facebook and while it's nice to know that a student thinks you're cool, they are under strict policy not to accept friend requests from students.

That makes sense.  You can never be too careful.  And those policies and probably there just as much to protect the student as they are the teacher.

I've heard some argue that it might be okay at a certain age or maybe if the student and teacher are of the same gender.   And someone once mentioned they thought a football coach should be able to be Facebook friends with a player.  One person even suggested that sometimes a student that's being bullied might be likely to reach out to a caring teacher using social media.

Are there areas where you think there should be exceptions to the rule?