  The relationship between the populations of optically and X-ray selected
Active Galactic Nuclei (AGN) has been unclear due to divergent results from
different studies. Arnold et al. (2009) claim that X-ray AGN are almost
entirely disjoint from optical AGN, while the Swift-BAT 70-month hard X-ray
survey reported that 553 of their 711 X-ray AGN are optical. In this work, we
set out to understand this difference by cross-checking between these studies
and examining their sampling and AGN-selection criteria. We also re-analyze the
X-ray and optical AGN in 16 groups and clusters reported by Arnold et al. using
our own optical spectrum fitting techniques. We find that 6 of the 8 X-ray AGN
in the Arnold et al. sample are also optical AGN, contrary to Arnold et al.'s
report that only 1 of the 8 X-ray AGN is also an optical AGN, thereby falsifies
their conclusion that optical and X-ray AGN are nearly disjoint sets.
