In a sign of the growing importance of e-commerce to major retailers, Target has become the latest merchant to end a relationship with Amazon that saw the latter providing e-commerce technology, customer service, inventory, site content and fulfillment of online orders for several major retailers during the past decade. Target, which has had a partnership with Amazon since 2001, said it plans to build and manage its own platform for Target.com, which it expects to launch prior to the holiday season in 2011.