Birds of a Feather Flock Together
Man’s tendency to live and move together as a group or community is an ongoing age-old concept. Within communities people tend to uphold basic accepted cultures and practices and to maintain considerable interaction; intensively active and dynamic communications.
The word “community” brings several definitions to mind. Let’s look at “communities” as subgroups of people, from within a broader population, whose members share specific ties and links. Herein rests the essential principles that reveal existing and possible communities. A population is not made up of a ‘random’ collection of individuals; instead it can be viewed as a collection of smaller communities (subgroups).
Traditionally, communities are made up of individual who live in the same region, speak the same language, share heritage and/or ethnicity, religion etc. Today, communities are made up, formed and evolving in unprecedented ways; crossing traditional boundaries and comprising members who are linked and interact in new and specific ways. The “online community” phenomenon reflects this range of development very well. How you decide to set, assess and target your ‘community of choice’ will depend on your available information, immediate objectives and end-goals.
Benefits of a community top down view. 
Communities from the inside out. 
Interesting people in the community.