I don't see the libpam-smbpass PAM module installed by default at all. I have checked the installs of my 10.04 DE installs. They do NOT have this PAM module installed at all. It is not listed in 10.10 or 11.04. These Samba packages do not list libpam-smbpass as a dependency or a part or the Samba 3.5.x package.