Is "Friending" a Teacher acting too friendly?

Many teachers use social media as a part of their classroom to enhance the learning experience, but not all social media teacher-student interactions have positive consequences. Many teachers have been called out for mentioning their students on social networking sites like Facebook (remember the teacher who called her students future criminals?). What rules should govern teacher-student social networking interaction? The Ontario College of Teachers has asked it's members to no longer accept friend requests from students. However they still advocate sites like Facebook as learning tools in the classroom. What's your opinion? Is it acceptable for a teacher to "friend" a student? Read the article here.