Investment firm William Blair & Company partnered with AdGooroo for a keyword-based advertiser-side analysis of the global search industry, authoring a report that pegs the number of advertisers at more than 500,000 and growing--with 90% of them currently running search campaigns with Google. The search giant didn't snag all available advertisers, however, as the report found that the 10% of marketers not using Google remained exclusive to either Yahoo or MSN. Analysts attributed this slice of market share to affiliate marketers and other companies whose business policies run afoul of Google's standards. According to the research, 30% of all search marketers run campaigns on Yahoo, while only 10% use MSN--with about half of each of their advertisers using Google as well. More ...