  There have been a number of forms of a conjecture that there is a universal
lower bound on the ratio, eta/s, of the shear viscosity, eta, to entropy
density, s, with several different domains of validity. We examine the various
forms of the conjecture. We argue that a number of variants of the conjecture
are not viable due to the existence of theoretically consistent
counterexamples. We also note that much of the evidence in favor of a bound
does not apply to the variants which have not yet been ruled out.
