  We point out that a conventional construction placed upon observations of
accreting black holes, in which their nonthermal X-ray spectra are produced by
inverse comptonization in a coronal plasma, suggests that the plasma is
marginally collisionless. Recent developments in plasma physics indicate that
fast reconnection takes place only in collisionless plasmas. As has recently
been suggested for the Sun's corona, such marginal states may result from a
combination of energy balance and the requirements of fast magnetic
reconnection.
