I've recently converted a website to html5 with the html5 elements (header, nav, article, etc.). Now, I am learning about microformats, rich snippets, etc., and I am a bit uncertain about why Google would need to be told that <nav> (in html5) is a navigational element using itemtype schema (SiteNavigationElement). The same is true of header (WPHeader), article, and footer (WPFooter). Also, why wouldn't Google understand that the first <h1> inside of my article is a "headline" or a "name" of significance? I guess I am just misunderstanding the need for much of the schema available. However, I can certainly see the need for some that perhaps aren't available (like registered trademarks associated with my website/organization/domain name).
From an SEO perspective, have any of you found value in providing the schemas above (even if the pre-existing on-page elements should've already told Google what the section(s) were about)?
I am implementing my markup slowly. So far, I've added the basic items mentioned above (and some of the limited schemas that Google's highlighter tool provides for articles). For those members with experience, can you suggest a few of the "critical" schema types that might be easy to overlook (or that made a difference in Google's valuation of your website)?
I may have some additional thoughts if this thread receives some replies -- I had other thoughts before I started typing, but they escape me now.
