> I would love to see this baked into a social network as a substrate for semi-structured debate.
Gaining insight and collecting disparate facts to form a bigger picture, an "argument map", with the ability for others to collaborate--that's exactly it.
However in addition to all the great use cases you've outlined, I also see potential for personal use, particularly in making structured decisions.
For example, purchasing decisions: researching to buy or not to buy widget X (in my case recently, sentiment analysis on stocks). With the creation of a simple browser plugin that allows you to highlight text and quickly add it to the map, it would make it easy to centralize all misc pieces of information supporting/rejecting a decision. Supporting "evidence" added this way will automatically link to the source, and optionally snapshot the page to ensure context of the particular supporting evidence is never lost.
I think it would be a fun project to create. If you ever think to actually work on this, or if you're interested in working on this together, let me know!