Microsoft's Bing search engine has overtaken Yahoo! search, digital tracker comScore reports, though the gap between it and Google's increasingly noticeable market dominance continues to grow. Bing had 15.1-percent of the core US search market in December 2011, the stat company says, putting it 0.7-percent ahead of Yahoo!'s falling share. However, Google rose 0.5-points to 65.9-percent, responsible for two thirds of the 18.2bn US searches made, and faces calls for FTC investigation for potential antitrust behavior.