I wanted to remove caribou (because xfce pops up an annoying dialog about it). But that in turn meant removing gnome-shell. No big deal I thought, I don't use gnome-shell. So I removed that too, and the next morning found out that gdm now gets stuck in a loop failing to load gnome-shell.
Should be fixed by https://admin.fedoraproject.org/updates/gdm-3.2.0-2.fc16 Also, this bug is a duplicate of bug #743596. *** This bug has been marked as a duplicate of bug 743596 ***