Abstract: 

The past decade has illustrated the dramatic importance of AGN feedback on the 
hot gas in groups and clusters. While these AGN are generally associated with
the brightest member of the group or cluster, AGN are also present in other
galaxies in these environments. I will present new results on the distribution 
of AGN in local group and cluster galaxies, as well as the evolution of AGN in 
dense environments out to high redshift. The demographics of local group and 
cluster AGN shed new light on the origin of nuclear activity in galaxies, as 
well as their ability to retain cold gas, while their evolution provides 
important new information on the coevolution of black holes and galaxies as a 
function of environment.