I'm very big on radically simplifying products by removing features that don't carry their own weight. But, without knowing what is being used, and how it's being used, it's a very painful process to do this when you don't know what's really going on. We don't have the data to back up our theories or decisions, so management (rightfully) balks.
We agree on quite a few actions like removing dead weight (here) or resisting “flying blind” (above), yet tend to disagree as to why and how we know. Cagan comes at this from a flat numbers will tell the truth viewpoint. Is it being used? If so, it is valuable. If not, it can be safely discarded.
I tend to look at things from a perspective informed by personas. What features are important to what personas and why? Having that lens first frames how to interpret the data.
