Websites are documents. In fact they are primarily what the web tech family was designed for. It fits well with the DOM concept. It was to facilitate a cross-platform way to display information to the world in a quasi standards based way. This does not mean the content is static but rather interact with the user to a certain extent. Dynamic content may displayed with JS or PHP. But the overarching idea of this category is to get information out. Examples are corporate websites & personal websites.
Enterprise business apps
These are full screen business tools. The concept of "website" is just not adequate. The app takes the full browser area, no header or footer, just a menu system, and a work area. These are really web implementations of what back in the day would have been full screen desktop business applications. Examples would be QuickBooks Online, Xero Accounting, Flex Rental Solutions, and thousands of other applications that fly unknown under the cover of the enterprise. The idea of directly using many of the web tools & technologies really shows their weaknesses here. Why? Complexity. The large enterprise app has a tremendous domain size and structure. This results in large numbers of components on the UI side. It's important in this area that the UI layer be self documenting in the form of packages (namespaces), component names, inheritance, and lot of the concepts on the backend that make development sane. Without structure, it literally becomes hard to find the component that you need to work on. In JS, there is no concept of class per file, so you can have many "objects" embedded within one JS file. That leaves you to a basic text search & find to be able to find your data (DTOs) & UI components. Bottom line, the large enterprise can implode in this space if a way is not found to manage complexity. And no Backbone is not always sufficient for this.
However, I want to look further. I find the concept of web abstraction compelling but I'm squeamish if it's really the long long term future. As in will it work well in 10 years. I feel that maybe the root problem of doing large Enterprise web apps is the DOM. I watched a youtube video (watch it, it's good) the other day about web frameworks and one guy made the comment something along the lines of "if you were to build a UI toolkit today, it would look nothing like the DOM". I find that fascinating. I feel the DOM is kinda a misfit for web applications but it has so much inertia going for it now, that it may be years before people start to seriously question the DOM.
Post-DOM is going to take a long time. I could easily see it being close to a decade before it reaches critical mass. In the meantime, I want to see awesome web abstraction tools. I think Vaadin & GWT have a compelling use case. I have reservations about Vaadin latency & performance but I think it's UI concept is solid.
To me, any good UI toolkit needs to be powerful but yet at the same time kinda just fade into the background and allow you to focus on solving business problems. You should not have to think about browser idiosyncrasies, compatibility issues, and structural complexity.
Cheers to awesome web abstractions, managed web complexity, and the post-DOM way of building internet applications whatever that may be!