In 2003, when oil was trading at about $30 a barrel, Andrew Hall, who was working for Citigroup's energy trading division Phibro at the time, was betting that oil would reach $100 within five years. So he bought a whole bunch of 'long-dated oil futures' that would only pay of if his hunch was right. And since his prediction seemed so far-fetched at the time, he got them cheap.
It was a risky bet. If the price of oil hadn't cleared $100 by 2008 (which it did) Hall would be out a bundle. But his hunch played out, and the Phibro division made more money that it would have had they just directly invested in oil ETFs.
Citi was supposed to pay Hall $100 million for the trade, but they didn't want to give him the full amount. The whole thing riled up so much controversy that Citi ended up selling Phibro.