There needs to be some connection, not necessarily interaction. Geographic proximity creates communities whether or not they interact, because the members have inherent shared interests. Something may arise that spurs interaction and action in concert. But the community exists already by virtual of residence by the members. It may be latent, but it's there.
Other relations between members are possible as well. Students and faculty at a university, for instance. Or staff and patients at a hospital. Or a regional technology interest group. In these cases, membership in the communities is more tenuous, and is maintained by group participation, enrollment in the university, participation in a hospital treatment program, etc.
Virtual communities such as HN are almost entirely reliant on interaction for establishing membership.
Other relations between members are possible as well. Students and faculty at a university, for instance. Or staff and patients at a hospital. Or a regional technology interest group. In these cases, membership in the communities is more tenuous, and is maintained by group participation, enrollment in the university, participation in a hospital treatment program, etc.
Virtual communities such as HN are almost entirely reliant on interaction for establishing membership.