Probably the "tightly-knit and reasonably homogeneous group" is going to appear in moodlenet in the guise of the communities as seen in the design sprint prototype...

I think it's true that this sort of group/ community could score resources to their own satisfaction, and it would be a useful time-saver for people who share the values and criteria of the community in question. Saving time must be a common aspiration among teachers.

Clay Shirky was very good on how communities have their own vocabularies for dividing up their worlds. But this makes me think that networks are always in danger of coagulating into separate groups who rarely enter into a discussion with outsiders. That way users miss out on getting different perspectives on a given resource, instead they have to start out by deciding which community they feel at home in.