  We briefly review recent developments in black hole accretion disk theory,
placing new emphasis on the vital role played by magnetohydrodynamic (MHD)
stresses in transporting angular momentum. The apparent universality of
accretion-related outflow phenomena is a strong indicator that vertical
transport of angular momentum by large-scale MHD torques is important and may
even dominate radial transport by small-scale MHD turbulence. This leads to an
enhanced overall rate of angular momentum transport and allows accretion of
matter to proceed at an interesting rate. Furthermore, we argue that when
vertical transport is important, the radial structure of the accretion disk is
modified and this affects the disk emission spectrum. We present a simple model
demonstrating that energetic, magnetically-driven outflows give rise to a disk
spectrum that is dimmer and redder than a standard accretion disk accreting at
the same rate. We briefly discuss the implications of this key result for
accreting black holes in different astrophysical systems.
