We haven't gotten our hands on a new Kindle Fire just yet, but we now know that Microsoft's Bing is the default search engine on the device's Web browser. Microsoft may have paid Amazon a pretty penny for the honor, one that could be important in Microsoft's longstanding struggle to wrestle search share away from Google.

The news was revealed by Ubergizmo, which snagged some hands-on time with the Fire at yesterday's unveiling. "The search box is powered by Bing," the author wrote, noting that she did not check to see if it's possible to switch to another search engine. We contacted Amazon, and have received confirmation that Bing will indeed be the default search engine. Amazon told us that users can switch to Google or Yahoo if they'd like.

Amazon also has a public statement on users' ability to choose the default search engine.

"All text you enter in Amazon Silk's address bar is sent to a default search engine," Amazon writes in the Amazon Silk browser terms and conditions, updated yesterday. "The initial default search engine is selected by Amazon Silk, and we may change the default search engine in the future without notice to you. If you would like, you may choose to use a different search provider as your default search engine. The privacy policy of the selected default search engine applies to information sent to it."

Google was previously the default search provider on the Fire. In all likelihood, Amazon is getting some money from Microsoft. Google is paying nearly $300 million to Mozilla over three years to be the default search in Firefox, for example, while a separate, sponsored version of Firefox defaults to Bing instead. We've asked Microsoft for details on its deal with Amazon, but the company declined to comment. Amazon also declined to say whether Microsoft is paying to be the Fire's default search, noting that "[a]s a matter of policy, we don’t disclose details about our business agreements."

Microsoft has never come close to catching Google in search share, but has put a lot of effort into making Bing smarter. Microsoft has also been trying to drum up some interest in Bing with a "Bing It On" page in which users can do a blind test to see whether they prefer Bing's results or Google's.

Amazon, as we reported earlier, is already putting ads on the home screens and lock screens of all Kindle Fires to boost revenue. Assuming Microsoft is paying well, Amazon may be making some good money on the Fire even before it ships.