BetaNews claims rapid updates and manageability gaps make Chrome and Firefox though the accept for large corporations:
In my experience dealing with businesses, it's rare to find them using anything other than Internet Explorer as their preferred web browser, and no surprise why. The other major browsers make life really hard for IT support. Whatever your opinion, it's way easier to support IE in an enterprise than Firefox or Chrome.
Firefox especially. It's old news that Mozilla doesn't have a manageable install version (a .MSI file) and they're not interested in creating one. This alone makes deployment and patching much harder than with IE, whose updates come out automatically through WSUS and other patch management systems.
So we already knew that Mozilla was uninterested in the needs of enterprise administrators, but just to make sure, Mozilla's Asa Dotzler (pictured nearby) announced as much to the public: Enterprise has never been (and I'll argue, shouldn't be) a focus of ours.