The Importance of Subscription Lines in the Financial Markets

There is no question that the increasing use of subscription lines is altering the pattern of draw downs and distributions. Some funds rely on subscription lines that are due on demand, rather than at the end of a stated term. What would be the effect if a large number of those lines were pulled simultaneously during a financial crisis? Or what if regulators required banks to call in their lines, even those that aren't callable or whose terms haven't expired?