According to Associated Press, a ginormous Reply-All storm nearly hosed the State Department's e-mail system:
WASHINGTON – Many "reply all" fiascos result in mere embarrassment, but American diplomats have been told they may be punished for sending mass responses after an e-mail storm nearly knocked out one of the State Department's main electronic communications systems.
This confirms that "Reply All" should be an obscure option buried under four cascading menus. It should be more impossible to find than your "edit signature" dialog. In a perfect world, you should have to manually copy the recipients from the reply e-mail body and paste them into the "CC" field. It should be that freaking hard.