In the opening session of #etmooc, there was some discussion around why a PLN instead of LMS.  There were some interesting points brought up, such as each participant having their own space and their own control.  This graphic caught my attention though:

Clearly it is meant to show how PLN is superior to CMS in terms of learning network size.  However, I don’t think it works quite like this.  There exists the idea that people’s social sphere and sphere of social interaction can only handle a limited amount of people. I’m sure there is decent research on this but I haven’t read it. I only know of this from Malcolm Gladwell’s book The Tipping Point.  I think people experience this in their daily lives with things such as Facebook.  Once a person gets a certain amount of “friends”, the signal to noise ratio starts to drop.  I guess you could say that we get information overload.  On the other hand, a CMS can result in a smaller, more manageable and concentrated cohort of people looking at achieving a common goal.

Having said this, I do appreciate the power of an expansive PLN.  My work (ie education) PLN consists of around 300 people via Twitter, and I refer and contribute to this community on a regular basis.