Why does mkinitrd fail with 'No module dm-mem-cache found for kernel' in Red Hat Enterprise Linux 5.3?

Release Found: Red Hat Enterprise Linux 5.3

Problem

By default the version of mkinitrd provided in Red Hat Enterprise Linux 5.3 attempts to include the dm-mem-cache module in the generated initial ramdisk images. Therefore when creating custom initial ramdisk images for kernels that do not provide the dm-mem-cache module, ...