Big deal. The same functionality already exists for previous versions of IE:
http://toolbar.netcraft.com/help/tutorials/using.html
The point is ... it's probable that most Firefox users aren't going to download Google's plug-in because they aren't aware of the threat of phishing -- or the applicability of the plug-in. IE has *built-in* that functionality. So, quite obviously, Firefox is playing catch-up. Regardless of what you think.