From the word gregarious "living in contiguous nests but not forming a true colony".
In the post MySpace era, where user blogs are the new web page, there will be all these small colonies of users with similar interests congregate but basically form clicks rather than communities.
Gregarian Societies are people who form clicks or groups around similar interests within forums or social networking sites. These can be seen in a Bands friends list, or TV Show's profile on a social network like MySpace or Facebook, and also in MeetUp groups.
Smaller groups or subgroups of like minded people in online communities or social networking sites.
If you were at a Band's/TV show's MySpace profile and you were viewing the band's friends, the group of friends/fans of that band are a Gregarian Society.