These three companies just didn't live up to Mr. Market's expectations last week. Sometimes an earnings stumble is a signal to sell, but digging in the dirt is also a good way to find turnaround candidates while they're getting beaten down.

It's a jungle out there today.

Pain and memory have been stilled
Our first underperformer this week is computer memory specialist Rambus (NASDAQ:RMBS). Expected to deliver a modest $0.02 of profit per share, the company reported $0.06 per share in losses instead. CEO Harold Hughes said he was looking forward to turning the business focus back to business again after a year of turmoil and backdating scandals.

That sounds like a great idea. The memory market is notoriously competitive, with memory prices nearly always in freefall and prone to cycles of oversupply and undersupply. Rambus has a finger in almost every memory chip sold thanks to a battle-tested portfolio of technology patents, and its fortunes rise and fall with the broader market's.

So this miss was perfectly understandable if you've followed the sector storyline through reports from Micron (NYSE:MU), Spansion (NASDAQ:SPSN), and others. But there's some light at the end of the tunnel, because some participants in this market have started reporting stronger memory prices at the tail end of the last quarter.

Beneath the city, two hearts beat
One example of that is Silicon Motion (NASDAQ:SIMO). $0.30 in EPS wasn't quite enough to please Wall Street, where the average estimate pointed to $0.32 per share. But the report also pointed to better times for flash memory, so the stock went up a bit the next morning despite the earnings miss.

Now, flash memory is a bit different from the kind of technology Rambus deals in. Never the twain shall meet, but their destinies are inextricably linked. Wherever there's some semipermanent flash memory, you'll find the volatile, short-term kind, too. Flash comes in larger sizes and keeps your data until you erase it, but the memory cells wear out after a few thousand write cycles. Standard RAM is smaller and forgets as soon as you turn off the power, but it's faster and you can overwrite it as many times as you like.

So your flash-based Apple (NASDAQ:AAPL) iPod or Research In Motion (NASDAQ:RIMM) BlackBerry comes with long-term flash storage and short-term DDR or QDR SDRAM, shunting flash patent royalties to Silicon Motion and RAM royalties to Rambus. The two share prices move in similar boom-and-bust cycles, but in a curious role reversal, Silicon Motion is smaller and faster, with much more volatility. They are both very interesting ways to invest in computer memory for hardware-averse investors.

Meet 'neath that giant Exxon sign
Nobody is exempt from missing the occasional target. As oil prices reach like the arms of God into a sky of soot and clay, you might expect good things from the big boys of oil and gas, and ExxonMobil (NYSE:XOM) is the biggest boy on the block by market cap.

Still, the company made it into this miss mix by undershooting the average analyst target by an ever-so-slight 2.9%. $1.70 in EPS fell short of the target by $0.05 per share, and it doesn't sound like much. $278 million might sound more substantial, but that's what 2.9% of $9.6 billion (the consensus estimate) comes out to.

As fellow Floridian Fool David Lee Smith explained, Exxon ran into a Venezuelan upheaval and declining oilfields, one of which is a short-term concern and the other looks like a long, slow death sentence for the entire industry.

Exxon and other oil producers may yet stay atop the current profit wave for years to come, but they need to plan ahead and find new energy resources somehow, whether by expanded drilling, Canadian oil sands, nuclear reactors, or harnessing the power of American Idol for the greater good. The wells will eventually run dry, and that day may be coming sooner than we thought.

All the way home
Some of these underperformers are victims of larger circumstances, while others might have only themselves to blame. It's up to you to decide which down-on-their-luck companies should be able to pull themselves up by the bootstraps and which really are stuck in the mud.

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Fool contributor Anders Bylund holds no position in the companies discussed this week, and he can't remember why. The Fool has a disclosure policy. You can see Anders' current holdings for yourself.