This is a handy summary of Wall Street’s woes:

…investment banks rely heavily on borrowed money, called "leverage" in financial lingo. Lehman was typical. In late 2007, it held almost $700 billion in stocks, bonds and other securities. Meanwhile, its shareholders’ investment (equity) was about $23 billion. All the rest was supported by borrowings. The "leverage ratio" was 30 to 1.

This looks like an inverted pyramid balanced ingeniously on the tip, not the base.

And really a lot of clever people thought it was stable (enough).

Hmm.

But this article contains this curious line:

This year, Lehman lost nearly $8 billion in "principal transactions." Otherwise, it was profitable.

Well, sure!

Most businesses who lose a feeble $8 billion would probably be more profitable had they not done so?