SAN FRANCISCO (CBS.MW) -- It's a retailer's worst nightmare heading into the week before one of the biggest shopping days of the year: losing advertisements.

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But that's exactly what happened to clients of Bizresearch.com, a marketer that helps merchants place advertisements on search pages like Google, Yahoo (YHOO: news, chart, profile), Microsoft's (MSFT: news, chart, profile) MSN and Time Warner's (TWX: news, chart, profile) AOL.

According to Laura Thieme, president and founder of marketing firm Bizresearch.com, her client's Internet search ranking was completely wiped out after Google recently changed its search algorithm that ranks Web pages based on search queries. For the last 18 months, Thieme's client, which sells board games, was ranked among the top 20 most popular sites for the search term "board games."

But after the mid-November tweak, the ranking didn't even make the top 800 listings. While the ranking fluctuated from time to time, it's "unusual to completely lose your position," Thieme said.

Other search-marketing companies noticed an abrupt change in the search rankings, as well.

"Google did something dramatic that influenced the database," said Andrew Wetzler, president of MoreVisibility, a search marketing company similar to Bizresearch. "There are a lot of people that had strong results (high placements), then all of a sudden didn't."

Throughout the years, Google has frequently changed or tweaked its algorithm to ensure relevance. Sites are relevant depending on how many people search or link to it.

Responding to the recent observation, and in some cases, criticism, a Google spokesperson would not comment on the timing of the algorithmic adjustment, other than to say that Google "frequently changes its algorithms to improve overall quality and accuracy of its search results. This is why it is common to see movement in the ranking of sites on Google search results pages."

Of course, Google's algorithmic search listings are free for a merchant. The lists are ranked based on relevance (however Google defines that), not on any monetary considerations.

To the extent that a professional service provider, like a doctor, or a retailer, like the board games merchant, received any ranking at all, it's free advertising. Why should anyone complain?

"There is obviously value to that traffic," said Scott Wingo, of Channel Advisors, which helps merchants sell or advertise on Amazon.com (AMZN: news, chart, profile), EBay (EBAY: news, chart, profile) and search engines. "So, it's probably better for them [merchants] to pony up for [paid] search [listings]. You're not entitled to a free ticket."

Timing is peculiar

But conspiracy theorists believe that the timing is too questionable to be just a coincidence.

Thieme believes that Google intentionally changed its algorithm to get merchants to pay to be listed.

Google's AdWords program, which is similar to Yahoo's Overture service, allows merchants to bid to be ranked under keyword searches. Merchants bid on the cost-per-click they're willing to pay for each visitor that Google sends their way. The more merchants or advertisers Google can get to be part of this AdWords program, the higher the cost per click paid to Google and its distribution partners, like Ask Jeeves (ASKJ: news, chart, profile). SoundView Technology recently issued a report estimating that Google's cost-per-click in the current quarter rose 7 percent sequentially. See Net Stocks: Jeeves to get Google boost.

As Google prepares to go public next year, as many expect, its does have an incentive to get merchants to pay to advertise.

What better time than the holidays to get merchants to pay up when they're most willing to spend for exposure. This would certainly give Google a nice fourth-quarter to slip into its S-1 filing, whenever it plans to file.

But the adverse consequences have left a bitter taste among those who rely on Google.

"Why did it happen a week before Black Friday?" asked a frustrated Thieme. "It couldn't have happened at a worse time."

Not only did her clients lose their rankings, Thieme has had to shift the budgets for certain campaigns towards more paid listings, and less organic. This leaves less in the budget that goes towards her services if she has to pay out to Google.

That's business some may say. But Thieme isn't alone in questioning Google's intent and motivation for the dramatic change.

Channel Advisors' Wingo agree that the timing of the algorithmic tweak is favorable for Google, to the extent that the reshuffling will drive merchants to pay for listings.

"The timing is kind of suspicious," he said.

But Google flatly denies that its rankings are motivated by anything other than the goal of getting the most relevant pages. "There is absolutely no connection between ranking on Google search results pages and Google advertising products. Google search results are objective and cannot be monetarily influenced in any way," said a Google spokesperson.

Many believe, including Thieme, that Google is, to some extent, conducting a maintenance check of sorts as it attempts to keep its listings relevant, and free of listings that are manipulated in order to get high placements. Indeed, cleaning up its listings is an ongoing battle for Google. Some companies set up server farms and duplicate Web pages in order get higher rankings.

Still, results pages aren't necessarily more relevant after Google tweaks its algorithms.

"Relevant is how Google defines it," said Wingo.

How will Google evolve?

This does raise the question of how Google's search listings evolve as it continually strives to be "relevant."

It may evolve into a list of educational and research information rather than commercial, according to Thieme. Already, she's noticed that many search results pages list dot-edu or dot-org sites or government sites.

Should this happen, then the merchants have no choice but to pay for an advertisement.

This could be a problem going forward as many retailers are losing margin by offering free shipping.

Take for example a company that wants to be listed under "board games."

Google charges 58 cents per click vs. 43 cent per click if a merchant worked with Yahoo's Overture. If a merchant had a conversion rate of 2.6, that means in order to get two customers from Google, the site has to get at least 100 clicks, at a cost of 58 cents per click, or $58. The average sale of a board game is about $35, said Thieme. That means two customers would generate $70, leaving the merchant with just $12 to pay for free shipping and all the other costs to run a business. That's not such a great business.

As Thieme puts it: "For retailers, the cost of advertising has just jumped substantially."

Market movers...

Meanwhile, it was a volatile day in the markets. Shares of leading Net names endured huge swings between positive and negative territories.

By the closing day, however, at least three of the leading Net names ended higher. They're still relatively unchanged for the month of December.

Other names were deep in the red, however. Akamai Technologies (AKAM: news, chart, profile) gave up 12 percent to $11.71. RealNetworks (RNWK: news, chart, profile) and Tivo (TIVO: news, chart, profile) were down sharply as well. Netflix (NFLX: news, chart, profile) gave up only 3 percent.

The Chinese Net portals, however, were higher. Shares of Sina (SINA: news, chart, profile), Sohu (SOHU: news, chart, profile) and NetEase (NTES: news, chart, profile) ended the day in the plus column.

They may come under some pressure in the coming days, however, depending on how investors view the upcoming IPO of CTrip, a China-based travel agency of mostly hotel rooms. Merrill Lynch is the lead banker behind this deal, which is expected to be priced next week. CTrip is currently on the road meeting with clients. The company heads for San Francisco on Friday.

Do merchants have reason to gripe about Google's algorithmic search? And, would you buy shares in CTrip's IPO? E-mail: Bfrancisco@marketwatch.com.

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