Microsoft's (NASDAQ:MSFT) Bing lost some zing last month, according to Nielsen's latest MegaView Search data. The aggressively marketed search engine started strong out of the gate after last year's launch, but it lost market share sequentially to Google (NASDAQ:GOOG) last month.

Microsoft isn't alone. All of the country's most popular search engines -- Yahoo! (NASDAQ:YHOO), AOL (NYSE:AOL), and IAC's (NASDAQ:IACI) Ask.com -- surrendered market share to Big G.

In other words, the problem may have less to do with Bing's shortcomings than with the strengths of market leader Google.

Company

Dec. 09

Nov. 09

Google

67.3%

65.4%

Yahoo!

14.4%

15.3%

Microsoft

9.9%

10.7%

AOL

2.5%

2.8%

Ask.com

1.7%

1.8%

Source: Nielsen.

Yahoo!'s perpetual fade is old news, and it will be interesting to see whether AOL's market share inches higher this month after the publicity behind its IPO. But whatever happens, I'm surprised to see Microsoft and Ask.com taking a step back in December.

Both engines seemed positioned perfectly to capitalize on the shopping-intensive month of December. Ask.com's seasonal deal$makeover and Microsoft's Cashback rebate program for online shoppers seemed like logical customer magnets over the holidays.

However, it's clear now that no one is going to slay Google. The company fulfilled a whopping 6.7 billion searches last month. If you're an advertiser, you can't generate paid-search leads without Google's platform.

Microsoft figured it may have had a shot by teaming up with Yahoo! last year, but it's standing on quicksand. Microsoft and Yahoo! combined for 24.8% of the country's searches last month, a significant drop from the 26% slice it commanded just a month earlier.

Consumers love underdogs on paper, but they lean on market leaders in real life. This is why Baidu (NASDAQ:BIDU) soared yesterday, when Google threatened to bow out of China.

Bing came in with its guns blazing last spring, but Google flat-out owns search in this country.

Will Bing bounce back? Let us know in the comments box below.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.