I use etckeeper, but only keep the repository locally. I use it so I can keep track of what changes there are to /etc, to help with that time when something breaks.
Clearly there are reasons to keep /etc/passwd in version control. Changes to /etc/passwd often need to be synchronized with changes to /etc/shadow.
For something like professionally administered servers accessible only via ssh asymmetric keys, /etc/shadow may not be considered so sensitive that it's worth the risk of having it be an exceptional cases in version control.
