Here is an excerpt from Beth Kanter's blog (which, BTW, is on using social media with non-profits - pay attention, students, as your final project fits the bill here!). This excerpt should get one thinking - and spark some conversation:
A traditional online community is a group of people who interact
together and have a relationship over time on a site where people can interact around a common interest. A loosely coupled online community is a group of people who are joined together by a common interest and have conversations is different - this might include groups on social networking sites or a network of blogs. It's important to determine if your organization needs a traditional online community or something else.