@cooper.semantics,
Let’s look at a theoretical header structure in a document from today:
h1
h2
h3
h3
h2
h3
h4
In this structure, you’d say the h1 was most important, but which heading is second? Probably the first h2, so we have our first clue: priority == precedence.
But, looking at it another way, the h1-6 headline structure only makes sense in the context of a single coherent document – it echoes the outline of the article.
But web pages today aren’t the single coherent document conceived of when the h1-6 hierarchy was invented. Instead they are collections of articles, ads, widgets, etc., that don’t fall easily into the old hierarchy. Instead of an academic treatise, web pages are now pages of a newspaper or magazine. The structure of the headings on the page, beyond perhaps the h1, is completely arbitrary. For example, if we decide all article headlines will be h2’s to indicate they are equal below the page’s h1, and widgets have h3’s, we break the outline structure implicit in the h1-6 hierarchy, by having h3’s with an h2.
Each item on the page really should have a right to its own h1, the starting point of its own outline, independent of the other items on the page.
Currently, we try to indicate priority by crapping on logical story structure in the name of page layout (thereby letting presentation issues dictate story structure, something most of us claim to be against). HTML5 reverses that paradigm, and allows us to maintain logical story structure for each of the several stories on the page, and leaves it to us to imply priority as best we can by precedence in the file.
Personally, I like having the choice. Since no one is forcing me to write one style or the other, if it’s important to me to maintain the logical structure of the content, I can write that in HTML5, and for those times I think I need to break that for presentation reasons, I can write that as well (multiple h1’s are only legal, after all, not mandatory). Either way, I win. ;{>}