An anonymous reader writes "The WSJ reports that Amazon's new secret weapon in its fight against other retailers is its delivery locker service. Dropping a package at a customer's door is not particularly secure, so Amazon Lockers were introduced about a year ago to provide a secure location for customers to retrieve their shipments. Now, Amazon is ramping up the service, opening new sites in the San Francisco Bay Area. From the article: 'Users don't pay extra to use the service but the locker program helps Amazon save on certain shipping costs. ShopRunner's Ms. Dias said UPS and FedEx Corp. FDX 0.00% charge retailers as much as 20% more to deliver packages to residential addresses because it is more efficient to deliver multiple packages to a business address. Failed deliveries are also more expensive for online retailers because those consumers are more likely to call customer service, switch to a competitor, or get a replacement item.'"