[create_account]

"there are no logically possible situations in the code that they haven't programmed a response for"

Until they blow up one day themselves...

Call me cynical, but no type system, no matter how sophisticated, nor team of programmers, no matter how talented & experienced, is immune to this type of thing.

[javert]

As I said, it helps make sure that doesn't happen.

Anyway, I don't think they'll blow themselves up big, like Dark Knight Capital did. First, this specific kind of thing doesn't happen often (where one firm just messed up so much that it makes world news). Second, it's clear from Jane Street's videos that they're pretty serious about quality. If I were going to bet on which market maker will screw up, it would be somebody else.

[kd0amg]

Sure, it doesn't prevent them from doing the wrong thing in that situation, but it does require that they have given the situation enough attention to write code for it, which is a serious improvement over not handling it at all. As I understand it, they play defense in depth with regard to code quality.