Exxon reported net revenue of $10.9 billion in the first quarter of 2008 -- the most profitable first quarter ever for the company, and shouting distance from the record $11.7 billion the oil giant raked in during the last quarter of 2007. But Wall Street deemed the results "disappointing" and Exxon's share price fell in early trading Thursday morning.

We could dwell on the seeming paradox of nearly $11 billion of profit putting a frown on anyone's face, but hey, it's always an expectations game, and Wall Street analysts expected more. Inside the numbers, there appear to be two problems.

The first is that while Exxon's crude oil business benefits from high oil prices, its refining and chemical production businesses do not -- instead, their margins get squeezed by the higher price of inputs. Diversification, in this case, is a mixed blessing.

But the second is perhaps more troubling. Exxon is reportedly having trouble boosting oil production.

Bloomberg reports:

Crude output from the company's wells dropped 11 percent to 2.47 million barrels a day, led by declines in Africa and Europe. Natural-gas production fell in the U.S., Canada, South America, Asia and the Middle East.

Perhaps Exxon isn't spending enough money on exploration and developing new wells -- CEO Rex Tillerson promised last month to significantly boost such spending this year. And no doubt, Exxon is still suffering from the nationalization of a key oil field in Venezuela.

Or perhaps there's just less oil to go around. When the biggest, most profitable oil company on the planet runs into trouble increasing production, that could indeed be construed as, uh, disappointing.