In the past I've commented on the mistake of building educational social media ghettos. My opinions were not popular with those who were funded to build edughettos.
I haven't changed my opinion:
Williams, S.A., Lundqvist, K., & Parslow, P. (2013). RedGloo: Experiences of developing and using an emerging technology in higher education. British Journal of Educational Technology, 44(4), 668-672.