Clay Shirky's essay, File-sharing goes local covers a really interesting progression. Firstly, "The RIAA is now attacking these networks using a strategy that could be called Crush the Connectors. A number of recent books on networks, such as Gladwell's The Tipping Point, Barabasi's Linked, and Watts' Six Degrees, have noted that large, loosely connected networks derive their effectiveness from a small number of highly connected nodes, a pattern called a Small World network. As a result, random attacks, even massive ones, typically leave the network only modestly damaged. The flipside is that attacks that specifically target the most connected nodes are disproportionately effective." Then Shirky highlights the reaction to this attack: from a global sharing system (Napster), decentralisation is introduced (Gnutella is client, server and router) but this has the effect of defining a subjective space: for performance reasons a search horizon is introduced. Next this horizon calcifies into a social membrane (the system adds a firewall to each application which requires an invitation to get through) and the fabric organises into social cells, each with its own filesharing ability.
Tom Coates remembered Microsoft's music-sharing-for-groups app Three Degrees the other day: Get into a group with your friends, share music by dragging it into a shared playlist (with shared controls); an icon (that appears the same on everyone's desktop) acts as a well to chuck around photos, and (what's more) winks -- little animations that go to everyone in the group simultaneously and just say "hi!". This is the way to go, certainly. Define a space that breaks up the global domain; within a local group get rid of space entirely and disallow direct person-to-person communication (unless the group has visibility of that connection). That's like rooms (real world rooms), like pub tables, like the way the world works. (Too much to say!)