Bing tasters have made a choice on the "decision engine," and Microsoft (NASDAQ:MSFT) isn't going to like it.

Web-analytics company StatCounter is reporting that Bing surrendered market share last month, for the first time since its zesty springtime launch.

Reality had to sink in eventually at Microsoft. Despite early raves, an ambitious ad campaign, and a defining paid-search deal with Yahoo! (NASDAQ:YHOO), Bing wasn't going to nibble away at market leader Google (NASDAQ:GOOG) every single month.

However, the drop-off is a bit startling, to say the least.

Company

July

August

September

Google

77.54%

77.83%

80.08%

Microsoft

9.41%

9.64%

8.51%

Yahoo!

10.95%

10.5%

9.4%

Source: StatCounter. (Microsoft includes Bing, MSN, and Live Search.)

It's not a shocker that Yahoo! is giving up market share. Once it announced that its searches would eventually be Bing-powered, it practically served up an admission of defeat. There is little reason to expect Yahoo!'s market share to recover, since it has what's pretty much a dead search engine walking. Its share stood at 12.57% a year ago.

Microsoft's slip is different, especially since it appears that the traffic that Yahoo! and Microsoft lost went right to Google.

Microsoft has still come a long way, though. A year ago, StatCounter had Microsoft's market share at 5.71%. Now it's battling with Yahoo! to see who wears silver and who gets the bronze medal.

This doesn't mean Microsoft should rest easy, though. If the larger Web-analytics companies confirm StatCounter's findings later this month, you can expect Microsoft to ramp up its Bing ads. It may also try to get its hands on Time Warner's (NYSE:TWX) AOL and IAC's (NASDAQ:IACI) Ask.com as smaller search engines that it can keep out of Google's reach.

Image is everything for Bing. The media was laying it on thick with the Bing lovefest until now. Now that the traffic appears to be slipping, will the media turn on Microsoft's spunky search engine?

No one other than Google and its shareholders wants to see Google become too powerful. Advertisers and Internet seekers need choices.

It's not a September to remember for Microsoft, but October is just getting started.

Bring on the next wave of Bing spots.

Google is Motley Fool Rule Breakers recommendations. Microsoft is a Motley Fool Inside Value pick. Try any of our Foolish newsletter services free for 30 days.

Longtime Fool contributor Rick Munarriz wonders whether it's time for Yahoo! to shed the exclamation point. He owns no shares in any of the stocks in this story and is also part of the Rule Breakers newsletter research team, seeking out tomorrow's ultimate growth stocks a day early. The Fool has a disclosure policy.