So it appears the gentleman in France who lost USD 7.3B had, as recently as 2006, been responsible for a third of the bank's annual profit..... to the tune of about USD 3B. The way he had found to accomplish this mad swing in fortune, both good and bad? 

His job was designated as a 'small profit' desk. He was to both buy and sell the same position, creating a small profit when the position actually moved in either direction. That was the job description. But initially, it appears his luck was good, and he began to take only one side of the position, immensely enhancing his profits. But as any trader will tell you, eventually your picks go south.....hence the huge losses. His excuse? His bosses "had to know" what he was doing and "said nothing to stop him" and so he continued.....

But I agree with Mike. You don't have losses until you sell. But that reminds me of a tax client of mine....he was the last person in 2001 to buy Worldcom. His daytrading consisted of buying 1 - 2 million dollars worth of stock, wait for the first 1/8 tick up, and sell. At that volume, the penny profit is large enough to make it worthwhile. He bought Worldcom at about $125/share, and waited for the uptick that never came. He rode that stock down to $2 a share, convinced the price would return to even greater heights. Wiped out the profit from 64 other profitable trades in one bad one.

Greed. That's the only word for it.

Or stupid.