OS X Mountain Lion changes the default save location for applications. Any app which support iCloud now displays the iCloud dialog as default when saving a document. With this default write command you can revert to ‘local hard disk’ as default location for saving documents.
defaults write NSGlobalDomain NSDocumentSaveNewDocumentsToCloud -bool false
Relaunch any currently running apps or reboot your Mac to have the changes take effect.
Revert to the default setting:
defaults write NSGlobalDomain NSDocumentSaveNewDocumentsToCloud -bool true
Screencast:
http://www.youtube.com/watch?v=uGTynT1SW2Y