I'm enjoying Lucas Gonze's intellectual development of the lightnet concept. To summarize, lightnets are Weblike (based?) networks for the distribution, linking, and editing of open continuous media, e.g. video and audio. Gonze has more technical definition, a strawman, and some examples of what contributes to lightnets and darknets.
A key emphasis is on "open" in both the media and tools. There are plenty of challenges here, especially in the face of massive, deep pocket, incumbents who already have a stranglehold on much of our culture. But this is a commons worth championing.
Then again, as Jon Udell finds out in his continuing tilts against the windmill, technical issues with making video and audio of the web are not to be ignored either.