The Gnome 3 Devs dumped the old
gnome-screensaver. The replacement screensaver is just a blank screen.
The Canonical Devs thought it was a useful idea to continue and raised a blue-print for implementation in Oneiric.
A few ideas were raised such as a Compiz specific implementation or reusing a Lubuntu/Xubuntu screensaver implementation.
However, at the time of writing, no implementation has been started.
Potential workaround - installing xscreensaver
sudo apt-get install xscreensaver xscreensaver-gl-extra xscreensaver-data-extra
Now remove gnome-screensaver
sudo apt-get remove gnome-screensaver
Now start the xscreensaver configuration tool - from a terminal:
or search from the Dash:
Click OK to both prompts asking to turn-off Gnome Daemon and to start xscreensaver-daemon respectively.
starting xscreensaver from login
Now to start the xscreensaver daemon on login you need to search in Dash for startup applications
Create a new entry running the command
Locking the screen
If you want to manually lock the screen with the keyboard combination CTRL+ALT+L then you will need to run the following to repoint the old gnome-screensaver lock to xscreensaver
sudo ln -s /usr/bin/xscreensaver-command /usr/bin/gnome-screensaver-command
Logout or reboot for all changes to take effect.