The next distinct interest to keep in mind is that of the business who will be powering their web site with your product. After all, they will be your customer and the ultimate beneficiary of your product's value. Like the end-user, businesses setting up shop on the Web are a unique breed. OK, me, too, but the reception of such attire at the event is the point here. Similarly, a shopping cart fitted with a narrow set of options will be of very little use to a company with diverse needs.
Every business is different.
Their products are different. Their policies and regulations on selling are different. Your shopping cart must be prepared to adapt itself to any possible set of circumstances. For example, let's use shipping costs as an example. My company has dealt with a client who sells bird-scare equipment to military, government, and agricultural installations.