  We analyse the scatter in the correlation between super-massive black hole
(SMBH) mass and bulge stellar mass of the host galaxy, and infer that it cannot
be accounted for by mergers alone. The merger-only scenario, where small
galaxies merge to establish a proportionality relation between the SMBH and
bulge masses, leads to a scatter around the linear proportionality line that
increases with the square root of the SMBH (or bulge) mass. By examining a
sample of 103 galaxies we find that the intrinsic scatter increases more
rapidly than expected from the merger-only scenario. The correlation between
SMBH masses and their host galaxy properties is therefore more likely to be
determined by a negative feedback mechanism that is driven by an active
galactic nucleus. We find a hint that some galaxies with missing stellar mass
reside close to the centre of clusters and speculate that ram-pressure
stripping of gas off the young galaxy as it moves near the cluster centre,
might explain the missing stellar mass at later times.
