Speculation is mounting about who will buy Ask.com when the "for sale" sign starts dangling from the struggling search engine's marquee.

IAC chairman and chief executive officer Barry Diller's description of the competitive search landscape has stirred speculation that the engine may soon be up for sale. He used words like "challenging" and "speculative" to describe the business during a recent earnings call with Wall Street analysts.

"We've been asked a lot whether we're open to consolidating transactions in the area of search. The answer is yes," Diller says, according to Search Engine Land. "And it is unlikely that we would be the consolidator."

"Microsoft would be very interested in purchasing Ask.com to give them even more market share against Google once Bing teams up with Yahoo," says Suzy Sandberg, president of PM Digital, NY. "This is by far the most plausible buyer. It makes sense for Barry Diller to sell Ask. With Ask being a distant No. 4, following Google, Yahoo, and Bing, it will seem even more distant after the Bing/Yahoo pairing."

The search market has grown extremely competitive. Formerly AskJeeves.com, IAC bought the search engine in March 2005 for $1.85 billion, but has failed to adequately compete with search engines supported by Google, Yahoo and Microsoft.

Aaron Goldman, managing partner at Connectual, believes Microsoft could become a suitor to take more market share. "Since launching Bing, Microsoft's market share has gone up less than one-and-a-half points," he says. "Meanwhile, Yahoo is down one-and-a-half. So it's a wash. With Ask, Microsoft could add 4 share points in one fell swoop."

Ask.com came in No. 4 with 3.9% market share in September -- unchanged sequentially, according to a recent comScore report. Google remained No.1 with 65% market share, followed by Yahoo and Bing with 18.8% and 9.4%, respectively.

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