Some examples of other lazy-loaded cases:

- If the editor starts up editing only one book (ie `/content/col123/m456`) there's no need to load all the other books/folders yet since they're not visible
- Images and other resources
- UserModel (doesn't exist yet but would  probably contain profile info, authored content)

Also, uniform lazy loading may be useful for other reasons.

**Aside:** My (wishful thinking) is an optimization where the initial page load would contain all the models needed to render the page inside the HTML.