Q: Is there a shortcut to turn dictation off?

see System Preferences->Dictation & Speech

The shortcut key will toogle dictation on and off.

On my system it takes up 8.5 mb according to Activity Monitor, that's not the enhanced version.

Additionally if the program is not active and Mavericks needs the memory for something else it will use its memory. So I  don;t see it being a problem if it is inactive.

But to answer your original question, no there is no shortcut to turning it on and off, at least that I can find. Seems to have to go through the Preference Pane. You could probably cobble together an Applescript to manipulate the GUI to do what you want.

reagrds

If all you want is a shortcut to turn off dictation this Applescript

tell application "System Preferences"

  activate

          set current pane to pane id "com.apple.preference.speech"

          tell application "System Events"

                    tell process "System Preferences"

 

                              tell radio button "off" of radio group 1 of tab group 1 of window 1

  click

                              end tell

 

                    end tell

          end tell

end tell

will do that. You could save it as an App and assign a shortcut to it.

Turning it on is a bit more complicated unless you have enhanced on already.