Ubuntu 9.04 offers the ability for Guest Sessions, through the User Switcher application docked on the top panel. This can be removed, if desired, by right clicking it and selecting Remove From Panel. With the User Switcher enabled, there will be no logout/shutdown/guest session or any of the other options available through the menu system. Removing the User Switcher yields a link to Lock Screen, Log Out [username], and Shut Down. However, there is no option for a guest session.
