The user stories are provided by the business. These stories tell the UXD team the "what", "who" and "why" of the design requirements. Based on the discussion or story time, the Business Analyst can come up with more relevant and detailed user stories. The UXD team can use card sorting for organizing the available information and identify different categories of the target audience.
A website is a good medium, through which you can reach out to customers in our information age. Unfortunately, many companies don't have this information sorted out. The result, customers are forced to waste their time searching. Sometimes, the information is placed so deep inside the layout, the customer just gives up, exasperated.
The concept of agile usability engineering is revered for bringing user experience (UX) activities to an agile environment. Both Agile and UX communities are increasingly warming up to the idea of working alongside to develop great applications fast. However, much work remains to be done and many challenges need to be overcome before the two teams can effectively work together.