Amazon.com Inc., in launching its tablet-computer battle against Apple Inc., is deploying a special weapon: technology that powers Amazon's popular website and that the retailer sells to other big-name Internet companies.

This technology, which the company said helps cut tablet-manufacturing costs, could give the retailer's just-introduced Kindle Fire device an edge over competing products such as Apple's iPad. But it may also spark new questions about customer privacy.

Amazon, best known as the Seattle-based retailer that started off selling physical books and music CDs, has developed a booming business unit over the past five years that is invisible to average consumers. Called Amazon Web Services, the division maintains a network of computers that store and deliver Amazon's catalog of digital books, songs and movies. Amazon also rents out this computing storage and power