+++ This bug was initially created as a clone of Bug #683723 +++ Description of problem: A bad Alt+F4 in a gnome-terminal window with multiple tabs open results in the terminal window being closed. I'd expect a confirmation dialog if there are multiple tabs open.
I kinda agree. Though, note that we close the window only if none of the terminals have anything other than the shell running in the foreground. At any rate, this should be reported upstream if anything.
As Behdad says, please file this upstream in https://bugzilla.gnome.org/enter_bug.cgi?product=gnome-terminal