  We use low-energy effective description of gauge theory/string theory duality
to argue that the Kovtun-Son-Starinets viscosity bound is generically violated
in superconformal gauge theories with non-equal central charges $c\ne a$. We
present new examples (of string theory constructions and of gauge theories)
where the bound is violated in a controllable setting. We consider the
comparison of results from AdS/CFT calculations to the QCD plasma in the
context of this discussion.
