Firefox users were up in arms over a Microsoft .NET extension that was silently installed into the browser without direct user approval. The extension was a bit tedious to remove for some people. At first the way to remove it was by editing the registry, which is not exactly user friendly. Microsoft later created a way to remove the extension without editing the registry.
Meanwhile some users revolted and even posted a bug report asking Mozilla to override an extension's attempt to disable its corresponding Uninstall button. Mozilla declined, saying that if they did that it would equate to manipulating a third-party application, which is what Microsoft did in the first place.
Nevertheless, another bug report is on file at Mozilla to hopefully correct the overall situation to at least some extent. People commenting on the bug are asking that Firefox alert the user when a new extension has been installed and offer the option to easily disable that extension. Without such a feature users might not ever become aware that something was added to the browser.
Seems a like a worthwhile feature to me. If you're interested in seeing this happen you can chime in over at Bugzilla