  Effects of disorder are examined in itinerant systems close to quantum
critical points. We argue that spin fluctuations associated with the long-range
part of the RKKY interactions generically induce non-Ohmic dissipation due to
rare disorder configurations. This dissipative mechanism is found to
destabilize quantum Griffiths phase behavior in itinerant systems with
arbitrary symmetry of the order parameter, leading to the formation of a
"cluster glass" phase preceding uniform ordering.
