  A discussion of the advantages and limitations of the concept of critical
balance, as employed in turbulence phenomenologies, is presented. The
incompressible magnetohydrodynamic (MHD) case is a particular focus. The
discussion emphasizes the status of the original Goldreich & Sridhar (1995)
critical balance conjecture relative to related theoretical issues and models
in an MHD description of plasma turbulence. Issues examined include variance
and spectral anisotropy, influence of a mean magnetic field, local and nonlocal
effects, and the potential for effects of external driving. Related models such
as Reduced MHD provide a valuable context in the considerations. Some new
results concerning spectral features and timescales are presented in the course
of the discussion. Also mentioned briefly are some adaptations and variations
of critical balance.
