When faced with the requirement of running several university sites, from a school to a museum, to share subdomains of a parent domain, and have separate domains. There are so many considerations based on details of how files and data are configured, how the sites will be managed, user authentication and site performance issues.
We have built multiple-site installations using many techniques, including relatively sophisticated configurations of the Domain Access module, Drupal’s multi-site feature, and other modules used to serve multiple sites.
PSR involves several sites that share the same infrastructure, creating an opportunity for all sites to share the same codebase.
Cloth Babies integrates multiple shopping carts and modules across a number of separate websites.
Metabolife runs several sites which share the same product catalog, and the same team to manage the orders, users, and products, even though the product catalogs and content are distinct for each site. The Domain Access module was the key component of this installation, allowing for apparently completely distinct sites to all run under the same Drupal installation.
Another use of the Domain Access module is found in the Row Eleven Wines wine study featured on the technical examples by the modules builder. Here multiple branded sites share a common shopping cart, on top of complex configurations of wine shipping by state and tax calculations.