Since Avi decided not to channel the antithesis of Kevin Costner in Field of Dreams (1989), I will! With the prompt of "How do we build/maintain digital cohorts and academic communities?" (or I'll rephrase it as, "how to build a community of dreams?"), I can't help but respond in a practical way.
It is extremely difficult to develop digital community without first bringing together people through an event. Most of the digital communities I've seen flourish start with a group of people who came together for some scheduled event like a conference, workshop, or webinar. The events help the potential digital community to both identify individuals as well as exchange digital contact information. For example, CyberSalon, the Google Group primarily made up of faculty who teach with technology in the Maricopa Community College District, started from monthly socials; now some people are only active on the listserve (especially those who do not live in Phoenix) and others are active in both the digital and real-world spaces.
However, identifying a potential community, and swapping contact information, is not enough. For the community to actually grow and thrive, participants must be active in the new "space" after the original event. And since everyone is always already busy, the new community must be providing something that makes it worth the member's time. This next spring, one of my classes and I will be work on this digital community membership and activity challenge while developing the "ODU Learns" social media plan for Old Dominion University's libraries, Learning Commons, and Student Success Center. The various academic learning services want to develop digital community to support ODU student learning. For example, the Learning Commons staff can regularly post pictures of students studying and working in the Learning Commons on the ODU Learns Facebook page. The learning commons provides something the students "want," and students join the ODU Learns Facebook page community. Once students are a member of that digital community, the students will be more likely to find, and hopefully to comment upon, the academic information the ODU staff will also be posting in the digital space.
Presentation poster about CyberSalon; larger image available to view on Flickr.