[SkyMarshal]

Worse dumb mistake I've ever made was to accidentally send a test email to several thousand live customers instead of the test accounts. That was a sinking feeling.

But creating a bug that loses your company half a billion dollars in thirty minutes and bankrupts them, must be stomach-churning.

[davidmr]

Much, much worse than the bug in the market making algorithms was the design failure of not having some out-of-band mechanism to kill order traffic (or of said mechanism's failure to be tested adequately).

This is a risk management failure much more than a programming error.