Comes now Greg Farrell, explaining how you've got a similar problem evaluating a bank:
Afterthought: Or is there less here than meets the eye? Farrell says that a bank's assets include "its funding commitments." Then he says the share price represents "the excess reservoir of capital that a bank can draw on..." Are these two the same? If so, the only (not very interesting) point is that the "funding commitments" probably don't show up as a balance sheet asset, even though they might be available as a matter of law. Much different if "the excess reservoir of capital" is something more than its "commitments"--e.g., perhaps its prestige or power in the market place, such as to impel people to lend it money even though they may not be bound to do so as a matter of law.
A falling share price at an investment bank isn't just a measure of personal wealth for employees and a metric to use when senior executives wanted to figure out when they could retire. When a bank hits hard times, there are no factories to sell or hard inventory that can be used as collateral toward a loan. The assets of an investment bank are its loans, its funding commitments, and the securities it holds. The share price represents the excess reservoir of capital that a bank can draw on aw a cushion against losses. At the worst possible time in [the history of Merrill Lynch, the brokerage/bank] when it was holding more than $30 billion of toxic assets on its balance sheet--enough to wipe the firm out--a plummeting stock price was shrinking the firm's capital base. It was yet another hole in the ship's hull.