I agree, there are cases where you would want a more robust client side data model, but, IMO people are a bit too quick to jump to using this and it can make more work in the end and make a project more costly to maintain. I think the cases where it is useful are mainly for highly interactive sites like those that would have previously done in flash, with animations (such as games, etc), for just regular CRUD webapps I feel its a bit of overkill