The most recent release by Google penalizes many e-commerce sites (including Magento) for non-structured keyword stuffing, poorly organized links and more. While Google’s rules can sometimes seem a bit arbitrary, this Vertical Response article is a great primer on the most recent releases of Google. It is especially relevant if you conduct a lot of content based marketing and optimize your eCommerce site for SEO.
http://www.verticalresponse.com/blog/google-penalties-all-you-need-to-know/
