Yes, all users should have an equal rights to access their e-commerce services. World Wide Web Consortium (W3C) has a document titled Developing a Web Accessibility Business Case for Your Organization: Overview (w3.org). There are four factors: social, technical, financial, and legal & policy related to Web accessibility & e-commerce. Since the Web is increasingly popular as
an essential resource for many aspects of life: education, employment, government, commerce, health care, recreation, social interaction, and more. The Web is used not only for receiving information, but also for providing information and interacting with society. Therefore, it is essential that the Web be accessible in order to provide equal access and equal opportunity to people with disabilities.
Need other resources?
Australian Human Rights Commission (hreoc.gov.au) has a more detail explaination on it. Read Working paper for e-commerce reference: web accessibility.
In practice and down-to-earth language, you may also visit Practical eCommerce website. There are some insights from Web accessibility, search engine optimization, search engine marketing, and other Web experts. They have some series of website review based on professional point of view.
eBay and National Federation of the Blind Partner to Increase Ecommerce Job Opportunities (finance.yahoo.com). Is it your business website next?