Hitwise has just released the summary of all U.S. searches conducted for four weeks ending March 27.  While we were not surprised that both Google and Bing's market shares went down, what's quite surprising is the fact that both Yahoo and Ask.com gained a significant percentage of  all the searches. Google search accounted for 69.97%, down from 70.95% in the previous month. Yahoo search increased to 15.04%, up by 3%, Bing search with 9.62% down by -1% and Ask.