Xubuntu: How can I avoid the double-password entry (lightdm then xscreensaver) on user switching?

I'm running Xubuntu raring with lightdm and xscreensaver. Both users on the system have xscreensaver set to lock the screen after n minutes. However, when I click "switch user" (or do gdmflexiserver --new), I have to enter the password first to lightdm, then to xscreensaver.

Since I can already do Ctrl+Alt+F7/F8 to avoid the lightdm password, shouldn't it be possible to avoid the password dialog for already logged in users? Xscreensaver will ask for the password anyway. Lightdm asking for a password that I can avoid seems like false security, while asking non-keyboard users to enter it twice is a hassle.