How do I remove 'Places' entries from the Nautilus sidebar?

^{Tested in Ubuntu 14.04}

Those bookmarks are controlled by ~/.config/user-dirs.dirs and commenting out a lines configures the appearance of the list

As an example, to remove the Videos bookmark from the list change the line:

XDG_VIDEOS_DIR="$HOME/Videos"

to

#XDG_VIDEOS_DIR="$HOME/Videos"

Note:
After login the file ~/.config/user-dirs.dirs gets reverted to the original set by /etc/xdg/user-dirs.defaults. To prevent that make the file "read-only" either by right clicking and then properties > permissions or using the command

chmod -w ~/.config/user-dirs.dirs

If you need to edit the file again do the opposite via Nautilus or use the command

chmod +w ~/.config/user-dirs.dirs

If you want to apply this to all users in your system change the file vim /etc/xdg/user-dirs.conf and set the option enabled to False. You need root permissions or this.

Open the file user-dirs.dirs in your ~/.config folder with your favorite text editor.

Comment out the line about the folder, which you do not want to be in the nautilus left pane. I commented about the Videos folder.

..........
..........
.........
XDG_DOCUMENTS_DIR="$HOME/Documents"
XDG_MUSIC_DIR="$HOME/Music"
XDG_PICTURES_DIR="$HOME/Pictures"
#XDG_VIDEOS_DIR="$HOME/Videos"

Then open a terminal, and run xdg-user-dirs-gtk-update, see the magic.

for 13.04 or later:

In Nautilus >= 3.6 this will not survive a logout/login or reboot. To overcome this we have to point our XDG directories to "$HOME" like e.g.:

XDG_VIDEOS_DIR="$HOME"

Aha - the definitive answer, thanks to A. J. McMinn: Removing entries from Nautilus Places

1) Comment out the unwanted bookmarks in ~/.config/user-dirs.dirs

2) Make or edit a ~/.config/user-dirs.conf file and add the entry enabled=false.

This solution persists over boot.

*...this could be done with a one-liner: echo "enabled=false" > ~/.config/user-dirs.conf

These directories are set by xdg-user-dirs.

Reading the documentation shows that you can disable a user directory by pointing it to your home directory. Use Ubuntu-Tweak or manually edit the file ~/.conf/user-dirs.dirs and point all the bookmarks you do not want to see to your home dir, and they will also disappear from the Nautilus side bar.

NOTE: I tried commenting out and removing the lines from ~/.conf/user-dirs.dirs as forestpiskie suggests, and that worked only until the next time I logged in. By setting them to the $HOME dir, the settings stuck.

1. Make the modifications you want to ~/.config/user-dirs.dirs like comment out the directories you don not want for example.
2. For the changes not to be reverted at login, you can execute in your terminal echo "enabled=false" > ~/.config/user-dirs.conf which will create the user-dirs.conf file containing the option enable=false.
3. Test the changes and their persistence by logging out and in again. Nautilus should display :

These steps still seem to work in 18.04. Based on comments in this thread I made the following bash script that performs the task. Note, you still need to restart nautilus and right-click remove the items after executing these commands:

nautilus_hide_unwanted_sidebar_items()
{    
    echo "Removing unwanted nautilus sidebar items"

    if [ "1" == "0" ]; then
        # Sidebar items are governed by files in $HOME and /etc
        ls ~/.config/user-dirs*
        ls /etc/xdg/user-dirs*

        cat ~/.config/user-dirs.dirs 
        cat ~/.config/user-dirs.locale

        cat /etc/xdg/user-dirs.conf 
        cat /etc/xdg/user-dirs.defaults 

        #cat ~/.config/user-dirs.conf 
    fi

    ### --------------------------------------
    ### modify local config files in $HOME/.config
    ### --------------------------------------

    chmod u+w ~/.config/user-dirs.dirs
    #sed -i 's/XDG_DOCUMENTS_DIR/#XDG_DOCUMENTS_DIR/' ~/.config/user-dirs.dirs
    sed -i 's/XDG_TEMPLATES_DIR/#XDG_TEMPLATES_DIR/' ~/.config/user-dirs.dirs 
    sed -i 's/XDG_PUBLICSHARE_DIR/#XDG_PUBLICSHARE_DIR/' ~/.config/user-dirs.dirs
    sed -i 's/XDG_MUSIC_DIR/#XDG_MUSIC_DIR/' ~/.config/user-dirs.dirs
    sed -i 's/XDG_PICTURES_DIR/#XDG_PICTURES_DIR/' ~/.config/user-dirs.dirs
    sed -i 's/XDG_VIDEOS_DIR/#XDG_VIDEOS_DIR/' ~/.config/user-dirs.dirs
    ###
    echo "enabled=true" >> ~/.config/user-dirs.conf
    chmod u-w ~/.config/user-dirs.dirs

    ### --------------------------------------
    ### Modify global config files in /etc/xdg
    ### --------------------------------------

    #sudo sed -i 's/DOCUMENTS/#DOCUMENTS/'     /etc/xdg/user-dirs.defaults 
    sudo sed -i 's/TEMPLATES/#TEMPLATES/'     /etc/xdg/user-dirs.defaults 
    sudo sed -i 's/PUBLICSHARE/#PUBLICSHARE/' /etc/xdg/user-dirs.defaults 
    sudo sed -i 's/MUSIC/#MUSIC/'             /etc/xdg/user-dirs.defaults 
    sudo sed -i 's/PICTURES/#PICTURES/'       /etc/xdg/user-dirs.defaults 
    sudo sed -i 's/VIDEOS/#VIDEOS/'           /etc/xdg/user-dirs.defaults 
    ###
    sudo sed -i "s/enabled=true/enabled=false/" /etc/xdg/user-dirs.conf
    sudo echo "enabled=false" >> /etc/xdg/user-dirs.conf
    sudo sed -i "s/enabled=true/enabled=false/" /etc/xdg/user-dirs.conf

    # Trigger an update
    xdg-user-dirs-gtk-update

    echo "
    NOTE:
        After restarting nautilus the unwanted items will be demoted to regular
        bookmarks. You can now removed them via the right click context menu.
    "
}

Edit -

Dug into it a bit further - if you edit ~/.config/user-dirs.dir you can remove them from the panel and still have them as folders in your /home it seems.

try going on Bookmarks in window menu, bookmarks > modify bookmarks (translate from italian ubuntu) and the remove the one that you don't want

otherwise Ctrl + D to access the menu