By Heidi N. Moore, contributor

If the markets were a TV sitcom — and really, they’re heading that way — the episode in which a drunk trader mistakenly bought millions of barrels of oil and raised the price of gas would certainly be the moment at which the whole show jumped the shark.

Consider the commodities shark fully jumped, as the world learned that the UK’s Financial Services Authority fined and banned former commodities trader Steven Noel Perkins for getting drunk one day in January 2009 and wreaking havoc on the oil market for a drunken trade. Perkins’ firm lost £6 million.

Perkins, however, at least had the excuse that he was drunk. Many other commodities investors in the second quarter didn’t. Almost all commodity prices have fallen. Oil prices fell 9%, zinc fell 25%, copper and aluminum are both down and wheat is also weaker. Those commodities that aren’t really suffering — including corn and soybeans — are experiencing intense volatility in their prices.

And, not surprisingly, the losses are setting in. Andrew Hall, the legendary trader who was paid $100 million by Citigroup (C), just ran into 10% losses in his new fund in May. The New York Post recently reported that JP Morgan’s (JPM) trading desk was rumored to lose up to $250 million on a bad coal trade in the second quarter.

Goldman Sachs (GS) research also shows that banks pulled back on commodities trading in May compared to their activity in the first quarter, which caused a drop in average daily volume in commodities trading by 7%.

Barclays Capital also said that assets under management by commodities funds fell by $3 billion in May, dropping to $291 billion, “with the fall in AUM due entirely then to price falls.”

It is starting to look a little tetchy out there. There are, however, optimists.

Gold prices are up and probably will keep rising. (Blame the spies.) Barclays is predicting new peak oil, with analyst Sudakshina Unnikrishnan writing recently that he expects 2010 to create the highest ever average level of oil demand and concurrent prices at $80 a barrel and above.

And Jim Rogers, the Buddha of commodities investors everywhere, is sticking to his guns. He recently said, “I’m short stocks and long commodities. If the world economy gets better, commodities are going to be the place to be because shortages are developing. If the world economy doesn’t get better, commodities are still a better place to be than stocks.”

The commodities bull run was a beautiful thing. But investors have to wonder whether the best trades have already been done.

–Heidi Moore is Sweeping the Street for the next two weeks while Colin Barr is on vacation.