This protocol could be implemented by services like Quora, Disqus, Livefyre, Wordpress, Stack Overflow or Drupal. I originally wrote it up as an idea for Quora, but realized it should be made more general.
1. Let's create a very simple document-oriented API with pub-sub. I use OPML for this purpose, but would be willing to support other formats if others want to. You like JSON, okay no problem.
2. People can use your web interface to create and edit public documents, with a twist. Users can also provide the URL of a document, and you provide me with an endpoint that I can ping when it updates.
3. Also support the flipside of the protocol as well. Provide a URL for the document, and are willing to ping a subscriber when it updates.
This allows the content to be stored where ever the author wants to store it, but for readers of your site, there's no difference. This would be the beginning of the bootstrap of a document-oriented Internet. No one captures or controls anyone's content. You don't have to export documents, because they never were imported. There are a lot of places we can go from here.
Another way of thinking of it -- a peering protocol at a much higher level than any existing peering protocol. Directly tied into the user interfaces of editorial tools. There would be an explosion of creativity among authors and developers. It's as big an idea as linking was when the web was introduced.
This really isn't speculative. We've been using the UI for this approach to editing for the web since the late 90s. I'm doing my third iteration fo it now. You just enable the feature if the user has an editor that can serve contant at 127.0.0.1. That's how you display the Post In Editor button. The editor can fully handle the conversation with the server. No spectulative technology here.