This is a very perceptive post, Scott. As more sophisticated Ajax-heavy javascript applications are developed, the desire for a thin server and fat client becomes stronger and stronger.

Oddly enough, it seems that with fat client webapps the latest craze in server-side web development, doing everything RESTfully, falls by the wayside first. You quickly get to the point where you'd like multiple updates and deletes across different client-side models to be synced to the server in the context of the same request, and to be able to take in a stream of server-side "push" updates (via polling or comet) and integrate them into the client-side models to keep everything up to date.

The next great javascript framework is going to provide a convention by which javascript models can parallel ActiveRecord ones, and when you update an attribute of a model in javascript, it does two things: Persists that change to the server, and fires off a notification (Cocoa-style) for any listening javascript views to update themselves. A large part of this work would be to figure out a data-interchange protocol for syncing client and server state that is flexible enough to emulate many restful requests inside of a single one, and promoting it with the aim of standardization.

Thanks, Scott.