The article is a bit sloppy, the filing linked at the bottom explains it much more accurately. NYSE didn't really 'choke' but the trading of some securities was affected. The root cause wasn't really a click or the flood of cancel orders themselves - it sounds like if the Credit Suisse system had actually managed to place all of its orders, the respective cancels would have been handled as well. What happened though is that CS<->NYSE got into an endless loop of spewing messages at each other because the CS end was simply ignoring the NYSE system's error messages and the NYSE system had no facility to detect a clearly abnormal rate of identical errors being generated by the same client. Bug met inadequately robust design and the whole thing imploded.
Traders are just like programmers, in that they often wish there was a 'Do What I Mean' instruction.
If you look for duplicated orders and request confirmation, the traders get mad that there are extra clicks keeping them from doing what they asked.
If you don't do it, the traders get mad when they make a mistake and it is dutifully executed.
If you do it only over a certain threshold, the traders get mad when they make a mistake that is large, but not over the threshold.
That said, I'm sure this sort of error has cost banks far more than a single $150k fine. The losses on a bad trade can easily outstrip that wrist-slap.
The losses on a bad trade can easily outstrip that wrist-slap
$340 million (eventually reduced to a bit north of $200 million) in one incident at Mizuho Securities in Japan back in 2006.
Word to the wise: There is a big difference between selling one share at 610,000 yen ($6000) and selling 610,000 shares at one yen.
Word to the wise, part #2: Nobody at the Tokyo Stock Exchange feels that they have the authority to cancel an order from Mizuho, even if Mizuho tries to sell a multiple of the market cap of a company in a single transaction. (This got regulators mighty pissed off, incidentally.)
