The energetics of high-Reynolds-number turbulent flows are usually thought to be unaffected by fluid viscosity if a region very close to solid boundaries is excluded. This basic principle leads to a number of explicit results, including the so-called logarithmic law for the mean velocity distribution. This talk will provide some background on some traditional results, explain a current controversy arising from ascribing a more direct role to viscosity, and discusses a simple way of understanding the essentials of the issue.