In Places->Recent Documents it lists recent documents on you ubuntu gnome.You may want to disable it because you don’t want other people to see in your list.
To clear the recent documents,just click on “Clear Recent Documents”.
To disable the recent documents feature,first create a file by following command in terminal
Then,edit the file by:
sudo gedit ~/.gtkrc-2.0
Add following,save and close the file
Restart gnome,the recent documents won’t appear anymore.