I belive that this is the future. With things such as Backbone.Sync written to communicate with websockets(via Socket.io). We can Keep Backbone models in sync easily.
Fog Creek's new Trello syncs data using websockets as well. Its quite effective and works well. Trello also falls back to a regular short-polling system if it needs to.
The Trello team loves WebSockets for push, and we did all of our initial prototyping and a lot of the first version doing RPC over the socket for writes and gets. However, now that we're supporting a REST API for other services to integrate with, we're moving everything other than pushing updates over to that so that we only have to support one API as we grow Trello's feature set. If we decide to go back to making requests over the socket, my best guess is we'll use the REST semantics and just send method, URI, and args in a WebSocket message and expect a response.
https://github.com/logicalparadox/backbone.iobind
Fog Creek's new Trello syncs data using websockets as well. Its quite effective and works well. Trello also falls back to a regular short-polling system if it needs to.