What do people think about using social media in education?

I cam across read an article, My Favorite Teachers Use Social Media: A Student Perspective, which believe that students will appreciate instructors' using social media in classroom and thus encourages instructors to do that. The article is quite common. But the following three comments are interesting.

All of the three comments indicate that people have negative opinions about the usage of social media in education. They think that (1) social media let people ignore real-life communication; (2) students dislike instructors using social media in education because of fears about instructors "stalking" them and performing not well; and (3) technology, including social media, fail to actually attract students' attention.

We are students majoring at instructional technology and thus are enthusiastic about social media in education. However, in most of other majors, social media seem to be seldom used by instructors. Moreover, many people hold similar opinions with the aforementioned three comments. These really give us challenges to design effective usage of social media in education and promote it.