  We discuss the virial balance of all members of a cloud ensemble in numerical
simulations of self-gravitating MHD turbulence. We first discuss the choice of
reference frame for evaluating the terms entering the virial theorem (VT),
concluding that the balance of each cloud should be measured in its own
reference frame. We then report preliminary results suggesting that a) the
clouds are far from virial equilibrium, with the ``geometric'' (time
derivative) terms dominating the VT. b) The surface terms in the VT are as
important as the volume ones, and tend to decrease the action of the latter. c)
This implies that gravitational binding should be considered including the
surface terms in the overall balance.
