I am not accountable
Faculty tenure is based on two principles: free inquiry and intellectual autonomy. Taken together, these principles also could be described by the less favorable sounding phrase "lack of accountability." A tenured faculty member simply is not very accountable to deans and department chairs [and, as Larry Summers learned, university presidents]. This absence of accountability, while it comes under heavy criticism, is part of the virtue of the university.
If you are interested in university governance, read the entire post. The lack of accountability really does describe how professors' jobs compare to most others'. I am not exactly sure who my "boss" is, but whoever he is, I go weeks or months without seeing him, and he has little idea how I spend my time day to day. I have often thought of professors as, in some ways, self-employed producers of intellectual output. That may be an exaggeration, but Cowen is surely right about lack of accountability being an unusual and perhaps defining feature of universities compared to other institutions.
By the way, Cowen is a graduate of the Harvard PhD program in economics and co-produces one of the most interesting econ blogs around.