The launch of Bing in June was Microsoft's latest volley in the battle for market share against Google. But it is working? According to a new report from search optimization firm SearchIgnite, not yet. Bing has had little impact on Microsoft's share of U.S. paid search advertising in the second quarter of 2009, the study found. In fact, Microsoft's search has remained at 6% of the ad pie, where is has been for years, according to the report.