Discussing justifications for the AIG bailout, two Washington Post reporters write:

[AIG’s] short-term debt is held by institutions all over the world, including money-market mutual funds, and its overnight collapse could have caused big losses in those funds, perhaps even risking a run on them.

These reporters need a refresher coure in Financial Institutions. Mutual funds have only shareholders, no debtholders. When a mutual fund incurs big losses, shareholders simultaneously lose some of their share value. Since the total value of the shares always adds up to the total value of the assets, there cannot be too little to go around for repaying shareholders, and those who cash out sooner do not get more than those who cash out later. There is no sense in any shareholder running to cash out. There is no "me first" situation.

Money-market mutual funds are somewhat unusual, it is true, in that they pledge to keep share price fixed at $1 per share (and distribute net earnings as increases in each customer’s number of shares). But a MMMF legally can, if necessary, break that pledge and reduce share price below $1 (or equivalently reduce the number of shares). There is still no prospect of a run. Even if all shareholders did seek to cash out, they all could.