E-commerce site duplicate content

Selected answers from the Dumb SEO Questions Facebook & G+ community.

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  Casey Markee: "Shared Content" can be just as damaging as "Duplicate Content." I`d advise you to take your entire site over and run a quick content report at www.siteliner.com. The tool will, among other things, pull out all the shared content and compares it to each other via percentage. If you have pages with "shared" percentages of higher than 40-50% then that would be cause for concern. I don`t need to tell you that the "best practice" for product variations is NOT to have their own pages. You have a root page, then modified attributes on those pages. And those attribute pages are not indexed or at the very least, have canonicals back to a root. So what you have described, from an SEO standpoint, not great out of the gate. That kind of setup tends to cannibalize traffic by pitting pages within the site against each other. And this is because duplicate content is a "between pages concept." Run the report, then see what you see.
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  Ammon Johns: There`s no such thing as a duplicate content penalty, so on that you can feel safe. However, Google does have page segmentation to determine which bits of a page are `boiler-plate` elements for the site, or even a directory within the site, and tell them apart from main content so it can weigh them differently. Ultimately, you`ll gain far more out of spending effort on adding valuable elements to pages (reviews, comparisons, demonstration videos and images) than from worrying at all about fixing duplication or near duplication EXCEPT if the duplication is preventing you getting all your genuine content indexed because too much crawling is wasted on duplicates.