A9.com, which went live on April 14, 2004, is an Internet search engine from Amazon.com. Its results derive from Google, supplemented by Alexa, Amazon.com and other engines for specific search types.
A9 has many features which many popular search engines lack. In addition to generic web searching, A9 has the ability to search the book results from Amazon.com that include "Search Inside the Book" (as long as a user registers with Amazon.com). If a user signs in, that user can view their search and click history. The A9 toolbar features a "search diary" designed to allow users to jot down notes about pages that they visit.
A9 is now out of its beta version, with a new color scheme. Its interface allows users to combine search results together, allowing side by side comparison of results.
A toolbar add-on exists for Internet Explorer and for Firefox, with support for other browsers under development. Mycroft offers an unofficial plugin.
A9.com uses many different search engines for specific uses:
The release of A9 was met with some controversy: some regard it as a trojan or as spyware. The features built into A9 record all of a user's searches and link them to the person's Amazon.com account. A9's privacy statement says:
- "We may, from time-to-time, employ other companies and individuals to perform functions on our behalf. Examples include sending e-mail and analyzing data. They have access to personal information needed to perform their functions, but may not use it for other purposes."
Some have speculated that A9.com will use data mining for targeted advertising (similar to GMail). People worried about their privacy can use Generic A9, which does not record personal information.
Those who use both A9 and Amazon (with cookies enabled) can earn a slight benefit of a 1.57% Amazon discount (at this possible cost of privacy). From the Amazon.com webpage:
- "Sponsored links revenue - from the small text-based ads on A9.com and Amazon.com search results pages - will help offset costs we incur through the Rewards promotion. With our automatic π/2% discount, we are effectively sharing with you some of the money we collect from sponsored links, i.e. sharing the pi."
In January 2005, A9.com added its "Block View" feature to the Yellow Pages part of its site, allowing users to view photos of businesses on many streets in over ten major U.S. cities after searching for a business name in that city. Users can also scroll up and down the street view (i.e., up and down the block, hence the name of the feature) in order to see images of other nearby businesses and the areas surrounding them. A9.com plans to continually add new images from a large number of U.S. cities. 
For more information see http://www.amazon.com/gp/xs/sharethepi.html