One of our customers uses a simple database to allow them to show stock levels and show details of special offers. This means that as well as their customers having up to date information, our customer doesn't have to pay for daily updates and they are able to make immediate changes to the site.
Another customer deals with the general public and government departments. Certain items aren't available to the public so by collecting user details from the site they can check who they are and who they are with. This information can then be used to mail newsletters and offer special promotions to individual users or type of uer.