If you try to use cifs to mount an smb share using the "users" option (making it possible for any user to mount/umount) cifs gets confused and shows this error message: 'username specified with no parameter'
fixed in more current mount.cifs and also in 2.6.10 or later kernels (may be even in earlier kernels). See project page for patches for some earlier kernels and mount.cifs.c is in SAMBA_3_0 tree