Currently debsums verifies md5 checksums of files
in a package. Would it be useful to have an option
to also verify the existance of files which do not
have a checksum, eg symlinks/directories.

For example /usr/bin/less is a symlink:

$ ls -l /usr/bin/less
lrwxrwxrwx 1 root root 9 Feb 23  2011 /usr/bin/less -> /bin/less

If this gets moved/deleted:

root# mv /usr/bin/less /usr/bin/less-moved

debsums won't report an issue.

$ debsums -s less
<nothing reported>

It would be possible to report an error in these cases
since details of this symlink is present in the .list file:

$ cat /var/lib/dpkg/info/less.list | grep /usr/bin/less
/usr/bin/less

If I understand correctly, this ticket is asking for a verification that
files without MD5 sums still exist. This is definitely useful, but at
least for symlinks, a robust checker would need to not only check that
they still exist and are still symbolic links, but that they still point
where they should. Of course, the contents of .list files are
unfortunately insufficient to check that.