There has been dramatic progress in the scope and power of plasma simulations in recent years; and because codes are generally cheaper to write, to run and to diagnose than experiments, they have a well-recognized potential to extend our understanding of complex phenomena like plasma turbulence. However, simulations are imperfect models for physical reality and can be trusted only so far as they demonstrate agreement, without bias, with experimental results. This "validation" process tests the correctness and completeness of the physical model along with the assumptions and simplifications required for solution. At the same time, it must be understood that experimental measurements are almost always incomplete and subject to significant uncertainties and errors. For optimum scientific progress, simulations and experiments must be seen as complementary not competitive approaches. We need experiments dedicated to answering critical questions raised by the simulations and which...