That could work -- if the JSON is intended for public consumption, and if it is documented as so. The problem, I'd argue, with JSON is that it does not intentionally facilitate semantic annotations, unlike HTML(5). I'd argue that a properly marked-up HTML5 representation of a piece of data is more useful than a bespoke JSON structure with crude naming liable to change without notice. The benefit I get with an HTML representation is that it's the exact thing that was intended for the user to read/consume, whereas JSON is awkward to divine meaning from without the crucial app-specific view-logic that turns it into DOM.
How would you reconcile the need for an open-semantic-web with arbitrary JSON structures with no governing semantic standard?
EDIT: An example of a potential problem: Please take a look at how the Bustle app you referenced brings its article content to the front-end:
E.g. http://www.bustle.com/articles/4470-why-we-should-root-for-l...
View source. It's not a public REST API (not visibly so); it's awkwardly embedded as literal JS in the HTML document itself... That'd be hell to publicly consume through any kind of automation.