I disagree with the idea that the HTML document, in it's initial state, should contain all the stuff that will be presented, if it's not necessarily going to be presented. If content requires the additional functionality that JavaScript provides in order to ever be visible, then I don't believe it has a place being in the raw document.

[In the context of a webpage at least, which I will always hold should be functional without JavaScript. I'm not talking about 'web apps' at this point. And I don't think that the backpack is (or needs to be) a 'web app'.]