The concept of "community" has always had two distinct meanings; one confined to living organisms and used by biology and the other referring to human beings.
As the term has evolved in its use in regards to the internet a hybrid of both meanings seems to be developing. On one hand the concept of an online community is, like biological one that defines a group of living organisms that share a populated environment and on the other a group of interacting human beings that share some common values and enjoys social cohesion.
With the internet I think the key is to determine how one turns the concept of community from the biological definition, or as nothing more than living organisms that share the internet to one that involves human beings with common values and social cohesion; from a petri dish to a neighborhood as I like to describe it!
The long term success of virtual communities will be predicated upon their ability to create a social cohesion; at some point large virtual communities will have to become federations; on line communities start from the top down and at some point their success will depend upon their ability to transform themselves into the opposite. The appeal of communities in the physical world is that they are personal because they all start from a basic unit; the family. From families neighorhoods are created, from neighborhoods comes towns and cities, from there come states, then regions and nations. The whole concept of social circles grows from the most familiar and intimate to the least.
Loyalty to the largest social circle starts from the loyalty to the smallest. If you look at Facebook, we know it is huge, with something like 700 million users, and it is overwhelmingly a success story. But its success is not really due to anything it has done as much as it is due to the fact that users have actually met, face to face, with 89% of the people who they are "friends" with. Thus, loyalty to Facebook is actually loyalty to the individuals who make up our social circle on Facebook.
I know one company that was a pioneer in the concept of communities and consumer centric business models. They have a community that includes millions of like minded individuals but when I go and track their physical communities I note that they have 363 and the vast majority of them are congregated in urban areas and their largest community has 137 members.
Well, some real quick math makes it obvious that they actually are a community of 22,000 (363 communities with an average of 60 members) rather than 1.5 million.
Of course they want to expand their 1.5 million by going international, and they should, but they need to also step back and realize that their long term success will be based upon increasing their 363 geographical communities, or their physical communities, rather than globalizing their petri dish. Communities are just as much about vertical growth, or the depth of penetration, as they are horizontal, or overall size.