“Think about it for a moment. A full 18 months have passed since the strange episode that caused the Dow Jones [.DJI 12227.89 -59.15 (-0.48%) ] to tumble 650 points in half an hour, wiping $850 billion off share prices, before rebounding. Since then, the issue has faded from view amid the eurozone drama.
But to this day, nobody has fully explained what really happened on May 6. Nor is there any evidence that the fundamental problems that caused the flash crash have been resolved. That leaves some scientists fearing that not only is a repeat of that flash crash possible, but it is probable — and next time round, it could be even more damaging.”
(Source: US, Asia, EU Business News: Flash Crash Threatens to Return With a Vengeance – CNBC.)