But before you climb into the trading pit, remember that your odds of consistently outsmarting the market's bet on the value of a bushel of wheat or a barrel of oil aren't any better than your chance of guessing what's next for Google.

The best case for buying commodities is for diversification. New research shows that a broad index of commodities futures can offer solid long-term returns, while in the short-term they can often rise as stocks fall (and vice versa, of course), lowering your overall volatility.

If that's attractive to you, you can buy an exchange-traded investment like iPath Dow Jones-AIG Commodity Index Total Return (ticker symbol: DJP), a Money 70 pick that tracks the return of a commodity index at a low cost.

Still, these new and complex investments are strictly for the advanced investor. Even then, it's possible that commodity returns will erode now that the big money on Wall Street has piled in.

"People become enamored of assets that are good diversifiers only after they've had higher than normal returns, which is when returns going forward are low," argues William Bernstein, author of The Intelligent Asset Allocator.

The bottom line is that commodities might be useful as a small part of your portfolio (think single digits), but they won't be a money machine that transforms your lifestyle.