An even more useful feature would be turning this off. If you haven't tried Duplicate Tab ( http://twanno.mozdev.org/ — aka, the first extension I install, every time, without question), I'd highly recommend it. It clones a tab either to a new tab or a new window (history included). This is the same behavior you see in IE, where a new Window is a duplicate of the current window. It's got a merge window feature, as well, where tabs from multiple windows can be combined in a single window and retain their history, but I rarely use that.

The sad bit is that the keyboard shortcut to duplicate a tab has always been Ctrl-Shift-T. Now, I can probably go through the Duplicate Tab code and change that, but it's since been ingrained.

I'm going to give the keyconfig extension a shot at altering the restore keys ( http://mozilla.dorando.at/readme.html ), as I saw nothing in about:config to even disable this restore feature, let alone alter it. This is, indeed, a handy feature, but it should be more visible (like bookmarking a group of tabs, but setting it up so that when you open that group again, it'll come with history) and configurable.