This is a website which provides links and resources for new and veteran middle grades teachers. The site provides links and information regarding many topics:
teachign strategies, maintaining student-teacher relationships balance, working with students from diverse cultures, newsletter, discussions, publications, etc.
This article is in regards to a school district in Florida which made it part of teacher protocol to not interact with their students on any social-networking website.
In my opinion, I think that it is inappropriate for teachers to "friend" their students. Inappropriate seems a little harsh to say but I do think that its better safe than sorry. Maybe once the student has moved on to high school and college it is okay to accept a friend request from them but even still whatever you post on the internet, you do it at your own risk.
I agree with Ashley, only I still think that even in high school I feel that teachers and students should not interact with one another unless it is school related. It seems that more often today teachers are getting fired or in major trouble by having some sort of relationships with there students. I know it doesnt just happen because they might be friends with them on facebook or something like that, but like Ashley said, "its better safe than sorry" and just stay away from temptations.