  [Oiii]{\lambda}{\lambda}4959,5007 "blue outliers" -- that are suggestive of
outflows in the narrow line region of quasars -- appear to be much more common
at intermediate z (high luminosity) than at low z. About 40% of quasars in a
Hamburg ESO intermediate-z sample of 52 sources qualify as blue outliers (i.e.,
quasars with [OIII] {\lambda}{\lambda}4959,5007 lines showing large systematic
blueshifts with respect to rest frame). We discuss major findings on what has
become an intriguing field in active galactic nuclei research and stress the
relevance of blue outliers to feedback and host galaxy evolution.
