This is more true for ecommerce sites where the products tend to resemble each other (e.g. diamond rings) and a deeper crawl is unlikely to make the results returned to searchers significantly better. Search engines also have that incentive in a WordPress blog context since a percentage of the newer posts likely rehash older ones, though the rehash is less pronounced relative to ecommerce sites.
I think of the blog as an extension to the website and gear the articles I write to talk more about the product. One other thing that I think helps is that on my sidebar I have links to our various web pages whether it is our signal flag horizontal banners, vertical banners and also our signal flag valances.
With Black Friday right around the corner, the holiday shopping season is rapidly shifting into full gear. According to Forrester Research, online sales for the 2011 holiday season are expected to hit $59.5 billion which would be a full 13% increase over last year. With this said, the 2011 holiday season offers online retailers significant sales growth opportunities.
A blog can reach into other search results (specific to blogs, articles, etc) and thus can affect traffic and reach into your target market.