semantics markup html css

So I took a look at the Drupal Markup Style Guidelines and one passage got me thinking.

If you're in doubt, put it in a div (and give it classes).

Don't leave content adrift on the page with no mark-up at all. Every chunk of html whether in a tpl file or a theme function should have a root DOM element. For module developers this is a div 95% of the time. In page.tpl.php it's the element. (or ?)