reports of Microsoft forcing Firefox extensions on users without their permission. If you're too lazy to click on that link, it all boils down to this. Windows Update, the automatic update tool will install an extension in Firefox without asking, one that will enable running .Net applications in Firefox. The problem is the uninstall button is disabled. Never mind the afront to the user, to install plugins for other programs they may never want, but the real chutzpah is to take away the user's choice to remove it.
(Supposedly there are removal instructions that involve editing the registry, which may or may not protect them legally, but from all practical points of view, it's not removable by the user.)
What's also really troubling is that this opens up the browser to all sorts of new vulnerabilities there used to not be. Up until now, if malware managed to get itself installed in Firefox, it was the fault of Mozilla, for not securing Firefox enough. Now, any bug in Microsoft's crapware is yet another vector to get junk into the browser and honestly, Microsoft's track record is far from stellar. Now, the only way to get a secure Firefox experience is to use any OS but Windows. This includes OS X, Linux, *BSD, Haiku, and many others.
Microsoft did this sort of thing once before, but to their own browser. They had this piece of technology, which even got them lawsuits, called ActiveX. If the very name doesn't have you shaking and crying for mommy, then congratulations, you must have been using Linux since 1991. For everyone else, we all know what kind of a failure that was, and Microsoft had no one to blame but themselves. This time around, if something goes wrong, they can just blame Mozilla. You might almost think that Microsoft is doing this on purpose.