For example, Vitanet is a site selling dietary supplements. The purpose is not only to sell the product, but to draw hits from search engines. The more text in your site, the bigger a target you present to search engines. One thing not to do, if you want traffic from search engines, is use software that generates your pages dynamically. Search engines don't index dynamically generated pages .
Most online stores can also profit by getting links from related sites.
The best way to get other sites to link to you is to give them a percentage of the sales generated by that link. Industry leaders like Amazon. Com have used this technique with great results. Put yourself in your customer's position. The sites you get sent to are the same ones your customers will get sent to, so those are where you want to start asking for links.