Errant Trades at Knight Capital Reveal a Risk Few Expected - NYTimes.com

A very expensive lesson on the importance of adequate software analysis, design, and testing

"But the firm ran up against its deadline and failed to fully work out the kinks in its system, according to people briefed on the matter. In its debut Wednesday, the software went awry, swamping the stock market with errant trades and putting Knight’s future in jeopardy.
The fiasco, the third stock trading debacle in the last five months, revived calls for bolder changes to a computer-driven market that has been hobbled by its own complexity and speed. Among the proposals that gained momentum were stringent testing of computer trading programs and a transaction tax that could reduce trading."

Errant Trades at Knight Capital Reveal a Risk Few Expected - NYTimes.com