Customer-written content, in the form of product reviews, community Q&A and shared stories, can both drive down search acquisition costs and improve natural search results.

Full article from Bazaarvoice CEO is here.
"For example, the term 'eye cream' returns 67,900,000 results; however, 'eye cream age 35' returns 206,000 results. While still a large amount of options, the more specific searcher has a better idea of what she wants to buy and is likely closer to making a purchase."
Screen Pages' e-commerce platforms are equipped with onsite reviews, which makes them EVEN BETTER for SEO, as the extra content is held on an additional product page (= two entries in Google's database) and you get extra copy for the robots to gobble up.