Ultra high-speed share trading
How some big banks are now making money - with high-powered computers trading shares in fractions of a second. It is highly profitable for the banks, but are there losers too? And cutting carbon - are the people who trade permits to emit carbon dioxide out to save the planet - or just to make money for themselves?
It's like something out of a James Bond film. A Russian-born computer programmer leaves a huge Wall Street bank taking with him - or so the bank alleges - a powerful, high-speed share-trading programme. The bank sounds the alarm and, two days later, the programmer is arrested.
Why all the urgency? Because, the prosecutor involved said, the bank told him there was a danger their programme could be used to manipulate markets.
That was back in July. Since then the programmer has denied any wrongdoing and though the bank involved in this case - the mighty American Goldman Sachs - has made no official comment, it's quietly putting it around that there's no reason to panic and that everything's under control. So why all the fuss?
With 30 years experience in finance behind him Professor Bernard Donefer of Baruch college in New York says the answer is simple: Goldman Sachs were afraid their secret computer trading strategies could fall into a rival's hands.
Talking about socially useful financial activity, you might think carbon trading would be top of the list. Because carbon trading is meant to cut back carbon dioxide - the major cause of global warming.
The concept is straightforward enough. Factories, offices, power companies and so on - get permits to emit the gas. These permits are then bought and sold and, out of that trading, in theory at least, carbon-efficient processes should gain while dirty ones lose out .
So what motivates the people who operate this and rapidly growing market? Are they out to save the planet? Or simply to get rich? As the BBC's Mark Gregory has been finding out, the answer may be a bit of both.