  In this paper, we examine in a unified fashion dissipative transport in
strongly correlated systems. We thereby demonstrate the connection between "bad
metals" (such as the high temperature superconductors) and "perfect fluids"
(such as the ultracold Fermi gases, near unitarity). One motivation of this
work is to communicate to the high energy physics community some of the central
unsolved problems in high $T_c$ superconductors. Because of interest in the
nearly perfect fluidity of the cold gases and because of new tools such as the
AdS/CFT correspondence, this better communication may lead to important
progress in a variety of different fields. A second motivation is to draw
attention to the great power of transport measurements which more directly
reflect the excitation spectrum than, say, thermodynamics and thus strongly
constrain microscopic theories of correlated fermionic superfluids. Our
calculations show that bad metal and perfect fluid behavior is associated with
the presence of a normal state excitation gap which suppresses the effective
number of carriers leading to anomalously low conductivity and viscosity above
the transition temperature $T_c$. Below $T_c$ we demonstrate that the
condensate collective modes ("phonons") do not couple to transverse probes such
as the shear viscosity. As a result, our calculated shear viscosity at low $T$
becomes arbitrarily small as observed in experiments. In both homogeneous and
trap calculations we do not find the upturn in $\eta$ or $\eta/s$ (where $s$ is
the entropy density) found in most theories. In the process of these studies we
demonstrate compatibility with the transverse sum rule and find reasonable
agreement with both viscosity and cuprate conductivity experiments.
