xscreensaver-extras has a dependency on xcreensaver-base, and xscreensaver-gl-extras has a dependency on xscreensaver-gl-base. This prevents xscreensaver-base and xscreensaver-gl-base from being removed when the xscreensaver-supplied screensavers are being used with gnome-screensaver. This causes two entries called "Screensaver" to appear in System | Preferences.
1. The fact that "removing xscreensaver-extras does not remove xscreensaver-base" is not only the issue on xscreensaver. For example there are many application rpms which split the library files into -libs subpackage for multilib issue (like abrt-libs, gimp-libs, ... ) and if you try # yum remove abrt or # yum remove gimp , these -libs subpackages are kept installed. There are also some game related packages which require "-data" package and remove the game rpms leave -data rpms installed So for this part, CANTFIX. 2. "This causes two entries called "Screensaver" to appear in System | Preferences" should be handled by gnome-screensaver (like F-11, F-10). *** This bug has been marked as a duplicate of bug 530318 ***
Ah, I misunderstood the part "This prevents xscreensaver-base and xscreensaver-gl-base from being removed", however anyway this is a dup of bug 530318, which must be treated by gnome-screensaver.