I'm amazed at the general lack of concern about rampaging energy prices' far-reaching effects on our economy. As last week wrapped up, FedEx (NYSE: FDX), one of the companies generally pegged as an economic barometer, raised another cautionary flag regarding fuel costs' impact on its operating results.

As I write this, the market is perfectly content with a slide in light sweet crude prices that still has the commodity above $123 a barrel. But investors should take FedEx's warning seriously.

For the quarter that will end with the last day of this month, the company's management now anticipates that FedEx will earn about $1.45 to $1.50 per share. That narrowed range compares to an earlier target of $1.60 to $1.80 a share. For now, it's left unchanged its full-year guidance of $6.40 to $6.70. If you think that range is staying put, I've got a bridge in Manhattan to sell you, cheap.

FedEx's latest warning follows UPS' (NYSE: UPS) cautionary comments less than a month ago that its customers have "tightened their belts." At the same time, UPS dropped its guidance by nearly 10% on the low end.

The delivery companies aren't the only ones suffering. Last week, the usually upbeat Toyota (NYSE: TM) said that, for a number of reasons, it expects its profits to slide by nearly 30% this year. It's beset by a stronger yen and the usual recent partners in crime: a week U.S. economy and rising raw-material costs. If those twin items sound familiar, look no further than General Motors' (NYSE: GM) most recent quarter.

Returning to the energy front, FedEx says its fuel costs have increased by $100 million just since its March guidance was issued. In that light, my investment advice regarding FedEx is to buy slowly if you must buy at all, and be prepared for a longer-than-usual holding period for the stock. This is a terrific company, but its operations are particularly susceptible to economic softness -- a malaise I think will stick around far longer than the market generally expects.

For related Foolishness:

FedEx is a Motley Fool Stock Advisor pick, and UPS has been tabbed by the Fool's Income Investor team. Find out more about these and other companies with a free 30-day trial subscription to either of these market-beating services.

Fool contributor David Lee Smith does own a pair of Toyotas, but he doesn't have shares in any of the companies mentioned. He invites your questions or comments. The Fool has a disclosure policy.