Ask most Americans and they'll tell you the oil markets are controlled by OPEC. But a recent lawsuit brought by four veteran floor traders alleges the global oil market is being manipulated from the waters off Scandinavia, not via the Middle East or Venezuela.

Specifically, ex-NYMEX board member Kevin McDonnell and three other floor traders allege BP, Shell, Statoil and the private trading firm Vitol are colluding to manipulate prices of Brent crude, the world's benchmark energy price.

At issue is that a relatively small amount of oil from the North Sea -- between 1.2 million and 1.4 million barrels per day -- is being used as the benchmark for the roughly 90 million barrels that are priced daily in financial markets, as Dan Dicker, a former oil trader and author of Oil's Endless Bid, tells me and Lauren Lyster in the accompanying video.

Dicker calls the traders' lawsuit "quite compelling" and says "to imagine this stuff doesn't happen would be a little naive."

There have been concerns about manipulation in the Brent market since the 1980s and at least six other U.S. lawsuits alleging price-fixing have been filed this year. As Bloomberg reports, they all have a common thread: North Sea oil producers are allegedly colluding with energy-trading houses like Vitol and Phibro Trading to submit "false and misleading information to Platts, an energy news and price publisher whose quotes are used by traders worldwide."

As Dicker notes, the energy manipulation allegations echo similar charges of manipulation levied against Goldman Sachs in aluminum and JPMorgan in electricity markets. Add to that the new revelations about investigations into currency trading and the massive LIBOR scandal of recent years and I'm reminded of something discussed here previously: Any market where prices are set by a group of individuals -- or a few companies -- rather than actual, exchange-based trades are highly likely to be manipulated.

"Proving it will be another matter, of course. But the outcome of the case isn’t the point," Dicker writes. "The point to me is again a clear example of how the commodity system, with physical control of commodity assets priced through financial vehicles like swaps and futures is a scourge that cannot assure anyone of legitimate prices. "

It shouldn't surprise anyone who's been paying attention that traders would manipulate markets if given the opportunity because the motives to do so are so compelling, as I wrote here last summer. And while these markets may seem arcane, they do have real world impact: LIBOR is the global benchmark for interest rates, including those on mortgages and auto loans; Brent Crude is the global benchmark for energy prices, ultimately including gasoline and heating oil.

The good news, as Dicker notes, is that regulators are aggressively pursuing allegations of manipulation, and have levied heavy fines against firms like SAC Capital and JPMorgan.

The bad news, he says, is regulatory zeal is pushing banks to get out of related businesses, leaving them increasingly in the hands of private firms who are unregulated and harder to sue, meaning the manipulation isn't likely to go away -- just underground.

Aaron Task is the host of The Daily Ticker and Editor-in-Chief of Yahoo! Finance. You can follow him on Twitter at @aarontask or email him at altask@yahoo.com