Thanks for the feedback. Sounds like we are all on the same page, tag repeated data with some sort of canonical reference. It seems using the itemtype="url" content="/product-name" would be the correct way. Here is what I am going with:
<div itemscope itemtype="http://schema.org/Product">
<span itemtype="url" content="/product-name"/>
Review Pages & Widget (nested in tags above):
<div itemprop="review" itemscope itemtype="http://schema.org/Review">
<span itemprop="url" content="/product-name/reviews/this-blender-is-great"/>
Same will go for any other nestable microdata tag that supports a url attribute.
I am still a bit worried that tagging every page with the root product will make the engines see every sub page as a duplicate. Hope this helps placement more than it hurts because it is a lot of work just to make bot engineers jobs easier, not to mention illegitimate
scrapers! Would hate to start seeing penalties (even non intentional algorithmic ones) due to microdata
From: Jason Douglas <email@example.com>
To: Robert Powell <firstname.lastname@example.org>
Cc: "email@example.com" <firstname.lastname@example.org>
Sent: Wednesday, October 31, 2012 11:18 AM
Subject: Re: Markup Spread on Multiple Pages
You can get the best of both worlds by consistently using itemid (microdata) or resource/about (RDFa) to point to the *one* canonical URL for the item (in your case /product-name, I presume).
That way you can repeat information across pages for snippeting purposes (like say the product name in the reviews page), while still clearly indicating that it's the *same* product being described.