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.

recent-document

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

touch ~/.gtkrc-2.0

Then,edit the file by:

sudo gedit ~/.gtkrc-2.0

Add following,save and close the file

gtk-recent-files-max-age=0

Restart gnome,the recent documents won’t appear anymore.