From SANS:
--Firefox 4 Will Incorporate Silent Updates
(August 6 & 9, 2010)
The next major release of Firefox will incorporate silent updating. Firefox 4 is scheduled to be released before the end of the year; two beta versions have been released in the last month and a third is planned for next week.
The silent update feature will be available for Windows versions of the browser only.
The feature will download and install updates without asking users' permission or requiring confirmation; such interaction will be reserved for major changes, such as updating from version 4 to 4.5 or 5. Users will have the option of changing the silent update feature back to the traditional, interactive format.
Google uses silent updating technology for its chrome browser; that automatic updater cannot be turned off.
The developers say that automated, silent updates mean more patched systems.
http://www.h-online.com/security/news/item/Firefox-4-to-include-silent-update-system-1052756.html
http://www.computerworld.com/s/article/9180272/Mozilla_plans_to_silently_update_Firefox?taxonomyId=17
[Editor's Note (Honan): Developers can claim that automated, silent updates "mean more patched systems," but developers need to realize
there are reasons for change control processes. Operations people will say that silent updates, if not controlled, can lead to network
disruptions and system crashes. Before rolling out this feature I hope Firefox will provide network administrators with a management tool
to control how these updates are applied within their environment.]