As stated above, there are numerous hours being spent on these sites because they are interesting and engaging. Personally, I too spend a good amount of time on social network sites. The only time I have utilized Facebook, Instagram and other social sites for class are in the current technology class. Moodle is utilized to convey assignments, announcements, and discussion group conversations. I believe social sites do not always have the capabilities needed to hold a full online class. I believe Blackboard or Moodle would need to be utilized.
When talking to my students, it would seem everyone has a Facebook, Instagram, vine, snapchat, or another social networking account. I am not sure how my students would like utilizing their personal Facebook account for class. I feel they might not engage because they do not want their personal profile revealed. At our school there are a lot of teachers who use blogs on their personal website for their class. I have found this is a good way for students to respond and stay connected to the subject and fellow classmates. Personally, I would not use social networking sites for my physical education classes. I would utilize it for the club I advise because I would be able to announce meetings, fundraisers, and announcements when necessary.
References
Buzzetto-More, N.A. (2012). Social networking in undergraduate education. Interdisciplinary Journal of Information, Knowledge, and Management. 7, 63-89.