Today, I did something equivalent, but far, far worse on the scale of aggravatingness. With lots of programs open, while attempting to click on "Force Quit..." under the system menu.... I accidentally hit "Shutdown" instead. Which my system very obligingly did, quickly and efficiently shutting down all my programs (including several windows full of tabs in Mozilla), all without asking me to confirm whether or not this is what I wanted to have happen.
I can't find a way to turn on a confirmation box for "Shutdown" anymore than I can for "Close Other Tabs." And the bugzilla debate over what to do about this particular issue doesn't look as if it's going anywhere at the moment.