Should Students and Teachers Facebook Each Other?

There is an ethical issue arising over how students and teachers should communicate online. On social network sites where oftentimes, inappropriate information gets shared publicly, a lot of incriminating things can be said. A student could divulge their partying habits, or their academic dishonesty.

And likewise, a teacher could get caught up in the fun too. When teachers can watch their students' social lives, and students and teachers have a forum to communicate privately after school, what are the dangers?

It wouldn't be proper for a student and teacher to be talking socially on the phone late at night, would it? So how should instant messaging, status updates, and other online communication be handled safely?

How is privacy affected when technology is so accessible and information is so public?