View Models and Yet Another Layer

Imagine that we could just transfer the data model our application uses, straight to the client. The client user interface can use this model, the same model the server-side components are using. What's the point? The shared data model, in theory, is a big win because you get at least some level of consistency. The view model is the representation of the application model I'm talking about here - it gets transferred to the client. A replica, as it were, of the reference model. The canonical model that any application components, client or server, should reference.