"The bigger they are, the harder they fall." It's the worst nightmare of every investor in today's market -- buying a rocket stock just before it takes a nosedive.

I readily admit that sometimes, stocks rise for a reason. But sometimes, the rise becomes the reason. No matter how often we caution them not to, investors do have a habit of buying "hot" stocks, and trusting momentum to keep 'em moving upwards.

Problem is, if the price goes up too much, even a great company can turn into a lousy investment (and if the company was less than great in the first place...) Below, I list a few stocks that may have done just this. According to the smart folks at finviz.com, these stocks have doubled (or nearly so) over the past year, and they just might be ripe to fall back to earth.

Companies

Recent Price

CAPS Rating
(out of 5):

McMoRan Exploration (NYSE: MMR) $16.79 ****
Universal Display (Nasdaq: PANL) $23.32 ***
Power-One (Nasdaq: PWER) $8.65 ***

Companies are selected by screening for 100% and higher intraday price appreciation over the last 12 months on finviz.com. Five stars = highest possible CAPS rating; one star = lowest. Current pricing provided by Yahoo! Finance. CAPS ratings from Motley Fool CAPS.

What does oil exploration have to do with organic light emitting diodes? And what do either of these things have in common with power conversion equipment? As it turns out, the companies behind these products are some of the Street's hottest stocks.

Shares of electrical power play Power-One are some of the topsy-turviest equities on the market, yet after a 12-month run, they're still sitting atop a better-than-150% gain. From its origins as a small-time supplier to Cisco, the company's evolved into a big-time play on solar power's success, capturing 11% of the solar inverter market. The company became a major "profit taking" phenomenon last month, when an electrifying earnings report confirmed that the company was doing every bit as well as its shares suggested.

In another sector of the market entirely, Universal Display suffered similarly to Power-One in the wake of its recent earnings report. Fellow Fool Anders Bylund can give you the lowdown on the quarter's news, but suffice it to say that while profits remain in short supply, sales are ramping nicely, and there's a good chance that Apple (Nasdaq: AAPL) will be throwing its support behind this technology soon.

In the here and now, CAPS members appear content to sit on the sidelines, assigning each stock a three-star rating that suggests neither huge risk nor great potential for profits. High tech is all well and good, they seem to say, but the real money is down low -- in the subterranean oil & gas wells of four-starred McMoRan Exploration. Let's find out why, as we delve into ...

The bull case for McMoRan Exploration
In case you're not familiar with the company, subsurfacemapper tells us that "McMoran is operator of a series of new discoveries and analagous prospects on the [Gulf of Mexico] shelf. I of course believe these will lead to profitable production in another couple years. I believe gas prices will be higher at that time. I further believe they have been unduly hammered by the BP disaster-the shelf will get back to drilling, but the deepwater (where they are not) may be permanently damaged."

Admittedly, offshore drilling has gotten a bit of a bad rap lately. Still, CAPS All-Star fluffybunnytr7 is a fan of McMoRan's "solid management ... great geology team, and ultra deep drilling from SHALLOW water make this one a sure winner."

A shallow-drilling specialist in a country filled with anti-deepwater drilling sentiment? CAPS member LifeForceDance exclaims: "drill, baby drill!"

No, baby. Don't.
I'm still not convinced. While McMoRan is surely an equal opportunity driller, happy to extract oil, gas, whatever it finds down there, most of its reserves are in the form of natural gas. With energy buyers valuing that gas at just $3.52 per million BTUs, this means McMoRan's 272 billion "cubic feet equivalent" of proven natural gas reserves are really worth less than $1 billion. Yet investors today are valuing the enterprise at more than $2 billion, or twice the value of its assets.

To me, this simply makes no sense. Why pay twice the value of its assets for McMoRan shares, when you could just as easily buy a bigger, safer, energy company like Chesapeake Energy (NYSE: CHK), ExxonMobil (NYSE: XOM), or ConocoPhillips (NYSE: COP) for mere fractions of their asset value? When you consider further that these three companies are all profitable dividend payers -- whereas McMoRan isn't -- I honestly don't see any attraction in this stock at all.

A better idea
If you disagree, you're welcome to visit Motley Fool CAPS and lay out a case for why we should buy this stock -- or, if you prefer, you can tell us about a company you like even better.

(Speaking of which, I just heard that the folks over at Fool Central have dug up a gem of a mining company that they like a whole heck of a lot better than any oil driller. Get a free report, and find out all about it, when you click this link.)

Chesapeake Energy is a Motley Fool Inside Value selection. Universal Display is a Motley Fool Rule Breakers pick. Apple is a Motley Fool Stock Advisor recommendation. The Fool owns shares of Apple and ExxonMobil.

Fool contributor Rich Smith does not own (or short) shares of any company named above. You can find him on CAPS, publicly pontificating under the handle TMFDitty, where he's currently ranked No. 613 out of more than 170,000 members. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Fool has a disclosure policy.