Microsoft’s online search has suffered a steady decline in market share over the last 12 months, 
while its biggest rival Google continues to grow.
The downward trend of Live Search, formerly called MSN Search, is reflected in figures released recently by three Web metrics firms: ComScore Networks, HitWise, and Nielsen/NetRatings. The site SearchEngineWatch plotted the monthly numbers for each of the top three search engines. With some hiccups, leader Google saw a steady increase in market share, and No. 2 Yahoo stayed about the same.
Commenting on Google’s gains, Bill Tancer, general manager of global research for HitWise, said Friday, "it’s very possible it could be at the expense of Microsoft."
Microsoft’s declining share is important because the company has made search a key component of its push to catch up with Google in the multi-billion-dollar online advertising market. Over the last several years, Google has reaped billions of dollars by selling text ads related to search results. Microsoft was late to the game, launching its AdCenter services for online advertisers in the United States in May. Yahoo launched an overhaul of its ad services in October. Microsoft Search Suffers Steady Decline In Market Share - Software News by InformationWeek