I couldn't quote the FHS, but I bet it says something about not having execultables in /var. Does /var/ftp/bin/ls "Change in normal operation"? Hell, given the recent reputation of wu-ftpd, maybe it does :-)
This is necessary. wu-ftpd issues a chroot() as soon as an anonymous user logs in for security reasons, so it can't access anything outside the ftp home directory (/var/ftp), including the normal ls binary. The internal ls feature of wu-ftpd is too experimental to use by default, so there's no way around it.
Erm... OK. Is there a chance that this might change mid-7.0 series? I'd hate to have to live with this for a full 18-odd months.