Customers walk out of Street Boutique, parked in Shirlington Village, Va. Street Boutique is a pop-up truck that's similar to the many food trucks in the area, except it sells clothes and jewelry. James Clark/NPR hide caption

itoggle caption James Clark/NPR

The Chicago skyline is reflected in the exterior of Neiman Marcus on Michigan Avenue in Chicago in a file photo from 2009. The luxury retailer sold for six billion dollars on Monday. M. Spencer Green/AP hide caption

itoggle caption M. Spencer Green/AP

A Nordstrom salesperson shows a customer an online selection of shoes on an in-store iPad. Like some other retailers, Nordstrom is using mobile devices to make on-the-spot sales and check companywide product inventory instantly. Courtesy of Nordstrom hide caption

itoggle caption Courtesy of Nordstrom