While the 'Flash Crash' of 2010 is unlikely to happen again, the stock market is still vulnerable to sudden and unexplained sell-offs, finance experts say. 'A lot of what has happened since the Flash Crash is what I would call proactive regulation,' said Maureen O'Hara, professor of finance at the Johnson Graduate School of Management at Cornell University. It was five years ago Wednesday that the Dow Jones Industrial Average plummeted almost 1,000 points in minutes, causing a world-wide panic among investors. Though the market quickly recovered, the causes of the crash are still being debated. TheStreet’s Scott Gamm reports from New York.