  We revisit the membrane paradigm calculations of the holographic shear
viscosity tensor of strongly coupled isotropic plasmas with Einstein gravity
dual by emphasizing the fact which was overlooked in the previous literatures
that the shear viscosity is a fourth-rank tensor. Using the membrane paradigm
we show that depending on whether the holographic shear viscosity tensor to
entropy density ratio is \eta^j_i^j_i/s or \eta^{jiji}/s or \eta_{jiji}/s, we
can derive three distinct formulae for the holographic shear viscosity tensor
to entropy density ratios given explicitly in terms of the background metric
g_{ij}. We find that the widely studied \eta^j_i^j_i/s holographic shear
viscosity tensor to entropy density ratio takes the universal value 1/(4\pi)
for isotropic background metric g_{ij} but \eta^{jiji}/s and \eta_{jiji}/s
holographic shear viscosity tensor to entropy density ratios take non-universal
values which depend on the details of the isotropic background metric g_{ij}.
