Most advertisers aspire to be number 1 on paid search and number 1 on natural search with a particular focus on Google since it typically drives 80% of search-sourced sales. Retailers in particular, though, may have noticed that for a wide array of products, Page 1 is actually dominated by Google Product Search listings and the CSEs, which push retailer-specific keywords down in the rankings, primarily affecting natural search listings.
Despite good intentions, there may be technical limitations, branding priorities and business rules that have prevented a retailer from optimizing their site well enough to jump over these sources. You may have also recently noticed that Twitter, YouTube, blogs and Facebook are all bumping down traditional, retailer-specific natural search listings even further.