Thanks for posting this site. It looks great! I have been doing this myself through Wikispaces but it was very time consuming to get a thumbnail shot of each site, upload it to the wiki, and organize everything.
Maybe overly simplistic definition - not really related to the academic theories but a starting point. Think it is too narrow to say they have been around forever -but 2.0 has changed things. Not that simple I feel. Learning has and is changing so the structure of what happens in a PLN is different.