Most of us know the general mechanics of digital social networks and there is plenty of conversation about digital community types and ways to manage digital communities
Each version of what they are, how they should be constructed, how they should be managed is nevertheless based on some prior assumptions. Prior assumptions are invisible, frequently undeclared and more often than not 'taken for granted'
These assumptions guide the advice that people give and the actions they take. Marketing people might 'see' digital communities different from, sales people, lawyers might understand them differently to charity workers. I'd like to suggest that these differences start from memetic differences. The idea of an extended 'memotype' is inspired by Richard Dawkins who came up with the idea that that artifacts and effects of animals in the real world are the result of the genes in the animal. The example he gives is Beaver Dam. The beaver's genes want to live on, they exist in the phenotype we call 'Beaver' and the extended phenotype is the Beaver's dam which is something it make to support having a family. See:
Memes (Dawkins' idea) being culturally transmitted ideas, that enable notions to leap from brain brain, might consequently have extended 'memotypes'. These are 'forms' of digital communities that are created based on the dominance of the memes at work in the minds of the people who produce them.
We can therefore characterise digital communities by their memotype. We could create a customers base, a prospect list, a value segment, a lifestyle segment, a co-creation group, an experientially connected group.
Each of these conceptions (memotypes) is developed out of the difference in memes that make them up. The implication is that there might no singular right way to construct a digital community. Each form depends on the needs of the community and the environment. Some will prefer Ning, others Facebook. Each is a memotype with paticular characteristics that serve particular puropses. Their continued existence will depend on relevence and evolutionary adaptability.