Starting with most likely the next Firefox 3.6.x update (currently scheduled for mid-October) the default set of Search Engine plugins shipping with Firefox will be changing. Microsoft’s Bing will now be included (user had to manually install this search engine plugin prior). Answers.com and Creative Commons are being removed, but can be installed manually by clicking the links here. Google, Yahoo, Amazon, eBay and Wikipedia are staying put along with any other search engines the user has manually installed on their profile.
Source: Mozilla Links