[dizhn]

If you have services with even a few users you should set up LDAP (openldap is fine) and then experiment with it.

LDAP is pretty old and very well supported overall. At one point I configured ldap for postfix virtual hosting. I chose LDAP rather than a database backed solution because of widespread first class support everywhere. The same directory later enabled me to use a ton of other things including SSO. You're always finding new ways to use it once you have it.

It's a great skill to have and is nowhere near as complicated as people make it out to be, including live replication.