Opera only uses the system gstreamer on Linux, on Windows (and probably Mac when they get around to it) they bundle their own gstreamer that only supports Theora.<p>I can see Firefox doing similar on Linux, so if it's just (ironically) the Linux geeks that are desperate for the patented codecs then I wouldn't worry too much about it. For the 60% of Firefox users on XP though, Mozilla aren't going to rely on system codecs that aren't there.