Everyone seems to be scared if they see walmart or target as a competitor. Yes these sites have high PR, but that is only the main domain. If you drill down to the product level you will see many of those urls have no PR and no backlinks and rarely any SEO optimization in the tags. Sometimes, they don't even have the keyword in the url, it will just say something like "product id=898992". Surely if you used hubpages which has as high a PR and as many domain backlinks as most retailers, put the exact keyword in the title and tagged it and backlinked the url, these would eventually outrank the retailer.