Don't feel bad, anonymous trader

The regulators are still trying to pinpoint the cause of Thursday’s Flash Crash, but one story doing the rounds (and, for the record, denied by the bank in question) is that a trader fat-fingered a big block trade of Proctor and Gamble stock, accidentally hitting the “B” key (for billions) instead of the “M” key (for millions).

This, unfortunately, happens. Here, from 2007, is a list of ten famously large fat-finger trades.

Among them: the Salomon trader who leant on his F12 key and sold a few hundred million dollars of French bonds; the junior trader at Mizuho who sold 600,000 shares of J:Com at one yen instead of one share at 600,000 yen; and this gem of a quote in relation to a fat finger at BoA:

“Rugby balls are a regular danger on any trading floor so the victim trader ought to have hedged against this possibility.”

Fat-fingers used to happen alarmingly often on the Tokyo stock exchange, which until January was saddled with a creaky old system that took five seconds to process trades, frequently went down for hours at a time and seemed to lack a “cancel” button. (The TSE famously admitted that Mizuho’s titanic loss on the J:Com trade - forty billion yen, or north of $400 million - was entirely the exchange’s fault.)