This "apps rather than documents" is hokum. Each time one of these JavaScript-mandatory websites is declared a case-study in web app development best practice, decrying progressive enhancement, there's normally something underneath about building a PhantomJS scraper so that search engines are indexing something more than a blank page.
> Are you saying that NAV etc. aren't valid semantics on applications?
What I mean is that the (supposed) benefits of semantic use of CSS classes go out of the window when you're no longer hosting documents to be read by machines. And the user does not care if the classes of HTML elements are semantic or not.
For example, bustle.com's PhamtonJS emulation of being a good webizen: https://twitter.com/tyleralove/status/367494129091346432
I like how people keep pointing to Google Maps as an example of Web Apps, and how web development best practice is outdated: http://www.fixmystreet.com/around?pc=SW1A+2AA