Yes, there definitely is an argument against it. And I'm sure they are wanting to help teachers avoid getting too close to their students, which would allow for inappropriate behavior. But I there's always a case against something. The fact that teachers were actually getting punished for it is on another level.

From my perspective it was quite useful. I myself sucked at remembering tests (because I was on here too much) and she knew it, she would just say "hey, don't forget our test tomorrow :)" and that helped me. She didn't have to do that but it was a nice gesture and it helped me remember.

When social media is new, people use it in curious ways that aren't best suited. The teacher/student friending was probably an attempt to relate to the student, or get in contact with them for homework/etc. As my mom is a teacher, I've seen some pretty interesting build-your-own-class-website websites, and Facebook could have just been another attempt at that sort of website, for the teachers.