How to tell if tag is "read" by any perspective view?

We’ve built our system to be completely “templatized” therefore we don’t bind directly to any tags. In an effort to clean up our tag database, we are curious if there is a way (programmatically or otherwise) to tell which tags are or aren’t being used?. It’s quite a large system, with 200,000+ tags and 600+ views.

I appreciate any recommendations/tips.