Christina, I know what you mean about needing time to process discussion topics and then reply. I think this phenomena is something different from the lurker phenomena (lurkers being another group of nameless, faceless students in a class), and I am now starting to wonder if there has been any research in this area. I find myself drawn to research in areas where I have a direct connection to the topic.
Tell me, as you mentioned you consider your virtual friends to be true friends, do you find yourself communicating with them outside of the initial point of contact? In other words, I do speak with a few SCoPE people outside SCoPE, but not too often in Facebook or Twitter. Vice-versa as well.