Metrics can be useful, but the issue I keep seeing in many areas is that they often become an end in themselves. And that's when they become dangerous. In law enforcement you see crime reporting twisted to keep certain "hot" categories low, in academia you see actual student learning subordinated to metrics based on five year completion rates and situations where resources are focused on the top 5% of students and the bottom 5%, leaving the average student in the morass of being "average" and thus not requiring resources.

A metric is a tool. Nothing more. Elevating it to a goal is dangerous, especially when you're using the wrong metric or trying to quantify something that can't easily be quantified (or shouldn't be quantified).