We just identified this same issue, and I'm glad to see that a feature request was already filed.
We are starting to encapsulate common functionality from our jobs into templates that everyone can reuse. The big problem with this approach is that there is no linkage between a particular template job and all of the users of that template. So, when I go to modify one of these common templates, I have no idea who will be impacted. We already maintain too many teams/users/jobs where a manual search would be impractical.
Also, just a quick note that this could be shown on the template job itself (just like upstream/downstream jobs appear) or as a separate functionality similar to what the Plugin Usage Plugin (https://wiki.jenkins-ci.org/display/JENKINS/Plugin+Usage+Plugin+%28Community%29) provides.