In large company environments they use a central directory systems to authenticate users against when users login onto a Linux/Unix or Windows box. Most likely the central directory service will be based on LDAP or Active Directory (of Microsoft). On the Unix boxes there is then a client install that communicates with this central directory service. It is mainly in such environments that adhocr is an useful and powerful tool.
See our adhocr project page at github
We were very pleased to be back on T-Dose 2012 presenting a rather small open source project adhocr and you can watch the presentation giving an introduction and explaining the usage of adhcor.