From giving Spire and Freebase a quick glance, none of these services seem to be designed to work in offline mode. What I'd love to see is a different kind of architecture: a server-less app with its local database (websql or indexedDB) which syncs with a server-side database instead of making RPC style calls. ie disconnected mode of operation with syncing when online.

This is how Meteor works from what I understand, and we've had to build this ourselves on top of Backbone for Post.fm. Perhaps we're a special case, but something tells me that the infrastructure of the future is not RPC calls but data-sync. (I guess MS Exchange is one of the first large examples of this).