  Observational searches for Intermediate Mass Black Holes (IMBHs), defined to
have masses between 30 and 300,000 solar masses, provide limits which allow up
to ten percent of what is presently identified as halo dark matter to be in the
form of IMBHs. These concentrate entropy so efficiently that the halo
contribution can be bigger than the core supermassive black hole. Formation of
IMBHs is briefly discussed.
