Virtual community

A theme that has been running though the course all semester, and, for that matter, throughout my years in grad school, is what do we mean by "community?" I'm not so sure we'll ever get a definitive answer, but the readings this week assert that some sort of interpersonal interaction is needed to establish a virtual community. Therefore, is a real-time chat feature essential to create a virtual community, or would discussion boards be sufficient? What other online technologies would be essential for a virtual community?