There are different levels of backstage, of course, and some of them are best left for tours, while others (such as those listed by
@_caleb) are best left unseen altogether. As for what one might view from outside the parks, I realise not everyone will share my perspective (indeed, most here appear not to), but I feel it's important to underscore that there are those of us who care deeply about theming but have no issue with (and may even be welcoming of) the kinds of backstage glimpses that others find so egregious.