I'm running Ubuntu 14.04 and when I select the shutdown option from the top-right corners drop down, instead of giving me an option to shutdown or hibernate, it only lets me lock and log out. I haven't made any major installations or changes to anything recently that could have messed that up.
The output of
gnome-session-quit --power-off is
** (gnome-session-quit:2707): WARNING **: Failed to call Shutdown: Logout has been locked down