It’s not just duplicate content that will affect where you rank it seems but Matt Cutts of Google’s Webspam team also wants to see you bring additional value. Based on interviews with him on the matter if you have the same content as another site just written differently Google will try to catch this and while based on other factors you might have ranked second to another similar page you could get knocked down off the first page.
If your SEO should have you on the first page and you can’t work out why you’re not this is something to look at then: for your SEO to work you want truly unique content and it is of course quite possible that you don’t even realize that other sites have happened to write very similar content to you; it could even be that they have copied your article, not duplicated but rewritten, but still come out ahead of you because their SEO is just a little better.
It may seem like a lot of work to go through each page and check if for certain key terms other pages have similar content but it could be worth doing: the other option of course is to focus your SEO on increasing Pagerank and other factors and you could suddenly jump up the rankings and other sites could fall right down.
What should you add to your articles though? According to Matt Cutts not just your opinion, how Google tell if you are giving your opinion or not is unclear and while some people’s opinions count it seems others don’t; presumably this is where Google’s use of Social Media comes in to decide who has a valid opinion and who doesn’t.
Another example of why you can’t ignore Social Media then and the importance of making your website itself a Social Hub. Extra facts and figures as well may help you with your rankings but e-commerce sites are among those who struggle most with this rule of Google’s.
If you search for a product in organic search, not product/shopping search, then you will not get just e-commerce sites, though these may seem the most relevant and may have the best SEO. The reason for this is Google like to show people a variety of different results for a search term, as a result often reviews come up too and pages with discussions on a product. The problem for e-commerce companies is they are generally given product information from the manufacturer and therefore have a limited number of facts that are almost identical to every other site selling the product.
Some e-commerce sites don’t even re-write a product’s marketing copy meaning duplicate content and no chance of ranking anywhere. To rank top though you either need the best pagerank and social factors from your SEO or need to add more on a product: you have the product so review it and mention any extra details you can: also get customers to review it as well not just to increase conversions but also to improve search engine rankings.