Online search volume grew overall in 2010 according to ComScore's 2010 U.S. Digital Year in Review. Search volume increased for all search engines by 12%.
The biggest gainer was Bing at 29%. The tremendous increase in Bing was certainly affected by the fact that Bing began to power Yahoo search. Google has a similar deal by providing search results for AOL.
Google's market share increased by 13% in 2010. The number of searches per user increased by 10% for that period.
Current marketshare of Google and Bing: