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Basically, it is a way for Google to block Bing aka Microsoft, and Yahoo, it isn't love for Mozilla. For that $300, Google gets to be the default search engine for Firefox. Microsoft and Yahoo were also interested in paying lots of money for the privilege. Think about how many people use Firefox, how many searches each of those uses make on an average day, and how much revenue is generated for the search engine as a result of being the one available by default. Even with Chrome, IE and Safari, among others, Firefox is the browser of choice for about 25% of users. Google didn't want that 25% going to other search engines, and I'm sure they wouldn't want people to get use to using Bing and thinking of it as what you do to look up something. "Bing it" instead of "Google it" would be a Very Bad Thing as far as Google is concerned.