Today, it was announced that Mozilla will include Bing in the third
position within our defined set of search plugins that we ship with the
en-US and en-GB versions of Firefox. [1]  Given Bing's significant rise
in both features and market share over the last year, we have entered
into an agreement to ship them.  eBay, Amazon, and Wikipedia will remain
in the list of default plugins.  However, we will be removing
Answers.com and Creative Commons from the integrated set, allowing users
to install those if they choose.

What does this mean for your locale?

Because you are the leaders of your locale, you are responsible for
helping us determine the best set of search plugins for your version.  
Presently, Bing is offered in 39 countries/regions/languages [2] and we
would like you to review it as an option if applicable.  The
l10n-drivers team will be filing a bug for each locale discussing this
issue and a couple other productization decisions you will need to make.
[3]  If you think adding Bing is a good idea, we should conduct the same
set of research we do for every plugin we ship, looking at any market
share numbers available that will endorse the decision.

What agreement?

Adding Bing to our set of plugins provides both choices and a user
experience that meets users' needs.  And, much like the agreements that
Mozilla has established with Google, Amazon, eBay and others, we will
enter into a similar revenue share with them.

What does it mean for privacy?

As some may be concerned about privacy, we took extra care to learn
about Bing's strongest privacy features and attributes.  Microsoft has
been helpful and eager to explain that Bing's search history features
are very easy to manage, with turn off and clear controls always
available.  The Mozilla team researching this decision also noted that
Bing has some of the most comprehensive anonymization technologies, and
has been front and center in the retention discussion across the
industry. [4]

If you have any questions, please just ask.  As always, it's a pleasure
working with you on this one.

All the best,

Seth

[1]
https://blog.mozilla.com/blog/2010/10/06/refreshing-the-firefox-searc...
[2] http://www.bing.com/worldwide.aspx
[3] The bug will discuss removing Bloglines, which is going out of
business, researching Bing, and looking at the removal of any search
plugins like Answers or CC, depending on your locale's preference and
research.
[4]
http://blogs.technet.com/b/microsoft_on_the_issues/archive/2010/01/19...