Google's worldwide gross revenue will total $11.8 billion in 2007, up from an estimated $9.3 billion this year and nearly double 2005's $6.1 billion and almost quadruple 2004's $3.2 billion, according to a new report from eMarketer. The "Search Marketing: Players and Problems" report examines the paid search advertising business and looks at Google's prospects as its driving force.

Google will account for 57.2 percent of all U.S. paid search in 2006, according to the report. That's up 32.9 percent from 2004. Yahoo's share of total U.S. paid search ad spend in 2006 is forecast at 27.0 percent, up only 4 percentage points since 2004.

David Hallerman, eMarketer senior analyst and author of the report, says "Google will increasingly require alternative channels to maintain its spectacular revenue growth. Marketers might very well be the beneficiaries of these alternatives, especially when it comes to still-to-be-realized potential growth areas such as local search, video marketing and classified ads."

The number of US search engine users is predicted to increase from 144.5 million in 2006 to 166.2 million by 2010 - that is, from 50.5 percent of the U.S. population (age 3+) to 56.1 percent.

Despite continued growth for the foreseeable future, search will have to contend with click fraud, consumer privacy concerns, and the complexity of creating and managing campaigns, according to the report.