  The ratio of shear viscosity to entropy density $\eta/s$ of any material in
nature has been conjectured to have a lower bound of $1/4\pi$, the famous KSS
bound. We examine string theory models for evidence in favour of and against
this conjecture. We show that in a broad class of models quantum corrections
yield values of $\eta/s$ just above the KSS bound. However, incorporating
matter fields in the fundamental representation typically leads to violations
of this bound. We also outline a program to extend AdS/CFT methods to RHIC
phenomenology.
