  Combined investigations of the clustering properties of galaxies of different
spectral type and high-redshift quasars strongly suggest local ellipticals to
be the parent population of optically bright Active Galactic Nuclei (AGN).
However, the picture gets more blurred when one extends the analysis to that
class of AGNs which show enhanced radio emission. Objects belonging to this
class in fact are found to be associated with structures which are about an
order of magnitude more massive than those that host radio-quiet AGNs. Also,
masses for the black holes engines of radio-enhanced AGN emission turn out to
be systematically higher than those which fuel 'normal' quasars. On the other
hand, the level of radio-activity in radio-luminous objects does not seem to be
connected with black hole/host galaxy mass, at variance with what found in the
optical case. These results, together with evidences for different cosmological
evolutions of different types of AGNs pose a serious challenge to all those
models aiming at providing a unified picture for black hole-powered sources.
