In a practical sense, assuming you are using a master page/rails layout on the server it would seem you'd want the content to be a single page, but that doesn't fly if you need to generate multiple pages to render a page.  So, seems the master page could not fully contain the header/footer of your overall layout, because you actually have to define page-specific dialogs *after* the footer, which seems weird.

Obviously you can slice up your master layout to put these things in different spots, it just feels unnatural to me.