It’s been three years since Amazon.com’s effort to match Google with its own internet search engine, called A9, crashed and burned. Since then A9 has largely fallen off the technology industry’s radar. But the unit is still around, and playing an active role in Amazon’s efforts to improve product search on its network of ecommerce websites.

“People say things like, ‘Oh, you used to work there. What happened to that?’” said Barnaby Dorfman, a veteran of A9 whose online recipe startup, Foodista, secured an investment from Amazon in April. “The public-facing experiment did not work out, but the other piece worked out quite well for them. They’re helping to maximize sales across all Amazon’s sites.”

While A9, based in Palo Alto, has been extremely quiet since Amazon pulled back on its web search efforts in 2006, its name has popped up repeatedly in recent months, providing a glimpse of Amazon’s evolving strategy with the search unit.

In June, A9 acquired a mobile startup called SnapTell that lets people take photos of items with their smartphones and match them to corresponding product images — technology that is central to Amazon’s efforts to let shoppers browse and buy items from their iPhones and BlackBerrys.

Amazon is also reaping a harvest of patents that were germinated during A9’s early years as a would-be Google rival. For example, Amazon on July 21 was granted a patent for a “System and method for providing search results based on location.”

That kind of broad patent could potentially have a huge impact on the mobile market, given that so many iPhone and BlackBerry applications today have location-based search features, using built-in Global Positioning System technology to direct users to local sights, restaurants, etc.

While it’s not clear what Amazon plans to do with the patent, it’s a sign that A9’s early work on search technology has resulted in some interesting intellectual property that could benefit Amazon in the future, giving it leverage in negotiations with other tech companies, for example.

Amazon spokesman Drew Herdener declined to make A9 executives available for an interview and declined to go into much detail about the search unit, saying only that it does “product search for Amazon.com sites and mobile applications.” He said Amazon does not comment on patents.

A9, on its website, says its product search efforts include Amazon’s Search Inside the Book feature that lets people search for terms within the text of books. The unit also works on the Clickriver Ads program that lets advertisers put sponsored links on Amazon sites (the A9 website also lists OpenSearch, an Amazon-inspired effort to create a standardized format for sharing search results).

Product search is a critical element of the online shopping experience. When someone searches for a product on Amazon.com, the speed and relevance of the results can prompt people to buy more and generate more sales. Amazon is also keen to adapt its product search to the iPhone and other smartphones, where more consumers are doing their shopping these days.

A9 has "moved from this very ambitious vision to something that’s a better fit for Amazon’s needs, which is searching for products,” said Oren Etzioni, a University of Washington computer scientist who founded Farecast, an airfare prediction tool. Farecast was acquired by Microsoft last year and its technology was incorporated into Microsoft’s new search engine, Bing.

A9 never made a big dent in the internet search market, which continues to be dominated by Google. For June 2009, Google had a 65 percent share of the U.S. search market, followed by 19.6 percent for Yahoo sites and 8.4 percent for Microsoft sites, according to internet measurement firm comScore (the data came out before the recently announced Microsoft Bing-Yahoo search partnership).

Amazon, which launched A9 in 2004, essentially dismantled the public-facing part of the search engine in Oct. 2006, removing its maps and block view function, its instant reward program, and search history feature.

The A9 unit is headed by Bill Stasior, a veteran of the AltaVista search engine. The A9 site says the unit is hiring for 10 positions, mostly in software engineering.

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