Firefox 4 will streamline and modernize the Web experience for our hundreds of millions of users. In addition to greatly improving performance, adding advanced graphics capabilities, and rethinking how people use tabs to organize their online lives, we have also been looking closely at the search options that we include in the search box, which appears to the right of the URL bar.
The current search options fall into three categories: general search, shopping, and reference.
Google remains the most popular general search and it will remain as the default search option, unless you change it. We will also continue to include Yahoo! as the second option for general search. Yahoo! has a loyal following and continues to provide a differentiated user experience, even as it integrates the Bing engine for its algorithmic search results. Bing itself offers a user experience that we think users will find valuable, and with its significant rise in popularity over the last year, we will also be including Bing as a general search option for English language users.
Amazon.com and eBay will continue to be included by default as popular choices for shopping search engines.
Wikipedia will also continue to be included by default as a popular reference search engine. We’ll be removing Answers.com and Creative Commons. Answers.com is a good service but we have found and we have heard from our users that Wikipedia is more useful as an included reference search engine. The Creative Commons search engine has changed over the years from one focused on locating CC licensed materials to one focused on providing a general search from Google, Yahoo! and others. We are huge fans of Creative Commons and will continue to actively support their organization and mission through grants and joint programs.
Overall these changes will mean that English-language versions of Firefox 4 will display the following search services, in this order: Google (default), Yahoo!, Bing, Amazon, eBay and Wikipedia. The choices available to our users will vary around the world. Localizers of Firefox will have the option to add Bing to the set of included search engines if they believe it is in the best interest of users in their locales.
Via Mozilla Blog