In the comments, Ryan Shaw points to the interesting MSMDX (Media Streams Metadata Exchange) project at UC Berkeley, whose goal is "to create a platform for collaboratively annotating, retrieving, sharing and remixing multimedia content.". It's just getting underway, but it has already produced one of the more cogent graphics illustrating the new architecture of participation in a remix culture.
This also suggests the start of a field guide to Long Tail producers of all sorts. Or perhaps a chapter. Hmmm.