At an industry conference on Internet search, Google and Microsoft engaged in a bizarre series of competitive barbs in which each accused the other of various indiscretions. But Google's claim was clearly the craziest: It says that Microsoft's Bing service is copying the top search results on Google Search, and it recently underwent a "sting operation" to prove it.

The allegation was made ahead of the Farsight 2011 show via Danny Sullivan's Search Engine Land blog. Sullivan says that Google briefed him about the copying charges, and he provided examples of identical search results in a blog post describing the incident.

"I've got no problem with a competitor developing an innovative algorithm," Google Fellow Amit Singhal said. "But copying is not innovation, in my book."

When contacted for a reply, Microsoft Bing Director Stefan Weitz said that Bing uses various "input signals" to help rank sites, and that Google Search is simply one of those signals. He then called out Google's "hack" as an experiment designed to "confuse and manipulate some of these signals."

So, how did this all come about? Last year, Google noticed that Bing search results were suspiciously similar to Google's. Google suspected that Microsoft's Internet Explorer (IE) web browser and Bing toolbars were feeding information back to Bing that would help the Microsoft search engine function more like Google's. So Google constructed a list of gibberish search terms and had employees pretend to search for the terms using IE and Bing on Windows. And over time, Bing would deliver the same results for these nonsense terms as did Google Search.

This is interesting enough as-is, but representatives from Google and Microsoft appeared onstage together at the Microsoft-sponsored Farsight conference yesterday after the allegation was aired. This was an uncomfortable event at which Google's Matt Cutts tried unsuccessfully to get Microsoft Vice President Harry Shum to admit to the copying.

"It's not like we actually copy anything," Shum said. "It's really about what we learn from the customers, who opt in to willingly share the data with us."

Cutts continually pushed the issue, to no avail. Shum called Google's assertion "a spy-novelesque stunt" and "a creative tactic by a competitor."

Undaunted after the conference, Google issued a statement attributed to Singhal that reads, "Our testing has concluded that Bing is copying Google web search results."

And of course, Microsoft has responded to that. "We do not copy Google's search results," Weitz claimed. "We use multiple signals and approaches in ranking search results. The overarching goal is to do a better job determining the intent of the search so we can provide the most relevant answer to a given query. Opt-in programs like the toolbar help us with clickstream data, one of many input signals we and other search engines use to help rank sites."

The really notable bit here, of course, is that it shows Google is concerned about Bing, and that Google is willing to be quite aggressive when it goes after a competitor, however small, that shows any sign of growth in Google's core market.