  In 1996, Accountability in a Computerized Society [95] issued a clarion call
concerning the erosion of accountability in society due to the ubiquitous
delegation of consequential functions to computerized systems. Nissenbaum [95]
described four barriers to accountability that computerization presented, which
we revisit in relation to the ascendance of data-driven algorithmic
systems--i.e., machine learning or artificial intelligence--to uncover new
challenges for accountability that these systems present. Nissenbaum's original
paper grounded discussion of the barriers in moral philosophy; we bring this
analysis together with recent scholarship on relational accountability
frameworks and discuss how the barriers present difficulties for instantiating
a unified moral, relational framework in practice for data-driven algorithmic
systems. We conclude by discussing ways of weakening the barriers in order to
do so.
