While Google remains far and away the leading search engine (with a 65% share of searches), Bing, at least according to Nielsen, is the fastest growing search engine.
Bing's search market share in August rose 22.1% to 10.7% of all searches up from 9.0% in July. It is important to note also that these numbers don't reflect Bing traffic alone, but rather MSN, Live and Bing combined.
So if Google (2.6%), AOL (1.8%), ASK (2.9%) and even Local.com experienced month-over-month search growth, was there an engine that didn't fare as well? You bet - Yahoo! - whose traffic in August fell 4.2%. Proceed to make assumptions on the reason(s) why, but it might have been caused by the full-scale introduction of Bing.