Unfortunately the Firefox folks also use it to prevent one from running older versions of Java and Flash, which is all very well except they block *all* versions of Java and now block last month's version of Flash as well. This is not helpful, especially given that I run the excellent Flashblock extension which replaces all Flash animations with a click-to-play button (and unlike the built-in Firefox feature, it actually works). Combining two click-to-play mechanisms doesn't end well.
Meh. Sledgehammer approach it is, as there isn't actually a security hole on my system (thanks to Flashblock and an anti-virus package). And at least I can still do this - the upcoming mandatory addon signing is not planned to have any override at all (which hilariously is a more locked-down approach than Internet Explorer!).