Brad,
There are lots of attributes you can have in an entry which
may help people search for an entry. However, only the DN will appear
in a certificate, and directiory schema (such at the NADF work) do not
encourage inclusion of these attributes in a DN. So these other
attributes do not contribute to authentication, in general, in the
same way as DN attributes. In the PEM environment, where we do not
assume ubiquitous directory availability, any attributes outside of
the DN do not contribute to authentication.
Steve