Another typical practice is to use both /bin/true and /bin/false. You put /bin/true in your shells (/etc/shells), and give /bin/true to all users who want ftp access, and /bin/false those you don't. This way, you can create non-interactive and non-ftp accounts for things such as email only accounts.
$Id: ftp_ohne_shell.html,v 1.2 2001/10/08 16:13:06 mic Exp $