They've completely disregarded the possibility that the lack of effective tab management is limiting most users to use only a tiny number of tabs.
Tree Style Tabs for Firefox has been an integral part of my browsing experience ever since I discovered it: http://i.imgur.com/PnpZwos.png
I just wish some browser vendor would release an official vertical tabs solution that had a more seamless implementation of autohide/autoexpand (for non-maximized windows where horizontal space is at a premium).