Good point I'll see if I can clear up that terminology in the post.

You are also correct that you could use the background page as an alternative persistance layer instead of LocalStorage. LocalStorage is obviously more applicable in non-extension environments. Is there a big benefit to using background pages in a Chrome Extension over LocalStorage simply for storage?

One thought for future work: load the Backbone app into the background page when the browser starts. Whenever the popup loads, simply update the Viewport view's element with Viewport.setElement() to be the root popup body element. This might allow persistance between popup loads.