When I perused the readings yesterday, I liked George’s continuum rather than Stephen’s dichotomy. But now that I think more about it…

I can, with some clarity define what groups I’m in.  (Male, English speaker, glasses wearer, etc.) Defining the edge of my network is more difficult.Even if you define strictly (my network is those with whom I have a bilateral following relationship on Twitter), your network is defined in terms of your relationships rather than a common shared state (those whom you follow may or may not be following one another)

I do think groups can be open. Take for example an open enrollment SL group.  You choose to be a part of it, but then are clearly a member of that group. Something like Deadheads is  trickier.  Since members of the group self select and identify (nobody defines deadhead until social scientists start researching them), finding the boundary of the group is difficult.  Nevertheless, my instinct wants to call Deadheads a group.