Because I’m currently seeing a forgotten logout screen, and have witnessed that a dozen of times now, with both GNOME and KDE (and Windows I think, too; but I rarely witness anyone using Windows…):

Please make the logout dialog automatically logout.

People tend to click on “Logout”, and forget about the usual “do you really want to logout, or maybe shutdown, or maybe reboot, or maybe …” dialog pretty much any operating system has.

I’ve never heard of anyone forgetting to pick “cancel” in that dialog, so I think you could safely default to the “logout” option after a timeout of 60 seconds or so. Just make it not leave computers unprotected (a screensaver will NOT activate!) for a long time just because people forget to logout twice.