The best thing about the stock market is that you can make money in either direction. Historically, stock indexes have tended to trend up over the long term. But when you look at individual stocks, you'll find plenty that lose money over the long haul. According to hedge-fund institution Blackstar Funds, even with dividends included, between 1983 and 2006, 64% of stocks underperformed the Russell 3000, a broad-scope market index.

A large influx of short-sellers shouldn't be a condemning factor to any company, but it could be a red flag from traders that something may not be as cut-and-dried as it appears. Let's look at three companies that have seen a rapid increase in the amount of shares sold short and see whether traders are blowing smoke, or if their worry has some merit.

Company

Short Increase Oct. 31 to Nov. 15

Short Shares as a % of Float

Marathon Petroleum (NYSE:MPC)

155.5%

3.3%

PVH (NYSE:PVH)

204.6%

4.9%

Sony (NYSE:SNE)

37.5%

1.5%

Source: The Wall Street Journal

One refined company
In 2011, when Marathon Oil (NYSE:MRO) was one of the first integrated oil and gas companies to announce plans to spin off its midstream and downstream operations so as to unlock shareholder value and give investors better earnings visibility, no one could have predicted that things would turn out this well. Since that spinoff in June 2011, Marathon Petroleum shares have nearly doubled. This rally, combined with the negative effects of Superstorm Sandy on refiners, has left investors wondering whether the good times can continue. While I'm not willing to enthusiastically say yes, I wouldn't bet against Marathon Petroleum here either.

Plenty of factors are working in Marathon's favor, including President Obama's plan to make the United States more energy independent and a lower but stable price of oil in recent weeks. A greater focus on U.S. energy independence will require greater pipeline and storage infrastructure, which is good news for Marathon's midstream operations, while its refining operations are benefiting from higher crack spreads related to lower, and more stable, oil prices. You might think Marathon has nowhere to go but down, but at just seven times forward earnings, I'm not betting against it.

Dressed to impress
PVH, formerly known as Phillips-Van Heusen, has been strutting its stuff on the runway for the better part of a year now. It's compiled a diverse portfolio of apparel and accessory names, including Van Heusen, Tommy Hilfiger, and Calvin Klein, and recently announced its intent to acquire Warnaco Group (NYSE:WRC) which makes intimate apparel and sportswear, to broaden its portfolio even further. But can it continue? That is a matter I'm not nearly as sure of, as international spending and currency woes could become a crippling factor that may stop its organic growth in its tracks.

In PVH's most recent quarter, announced last week, it noted a 24% increase in profits, even as revenue declined 1% thanks to a negative 5% impact from currency translation, as well as exiting from a few discontinued businesses. Gross margin did expand by 260 basis points due to higher selling prices in Calvin Klein and Tommy Hilfiger, but it's clear that overseas customers will only deal with so much of a price hike. I fear we are close to a near-term peak in PVH's share price and am considering entering an underperform CAPScall on the company within the next couple of days. In the short term, I'd say short-sellers have every right to be skeptical, especially with its international exposure.

Get the bagpipes
There are a lot of severely troubled companies that look like they have an opportunity to turn things around through innovation and cost-cutting. Best Buy, Staples, and Dell, just to name a few, could be big surprises in 2013. Sony, on the other hand, looks like it's about to fall off the innovative cliff.

At one time Sony was among the premier names in the electronics industry, commanding premium pricing power on brand name alone. Then, Sony became complacent and the competition simply out-innovated it. What we're seeing now, with eight straight years of losses from its television division now in the books, is a combination of oversupply in the electronics space and Sony's own hubris of producing premium-priced electronics getting in its way. Sure, Sony has had some nice OEM contract wins, including the contract to supply the camera for the Apple iPhone, but the victories have been few and far between. At some point you have to ask when enough is enough, and following a massive writedown this year, I'm willing to raise the white flag for Sony if it won't do it itself. Short-sellers, have your way with this stock!

Foolish roundup
This week's theme is all about sustainability. Aside from Marathon, which even leaves me skeptical to some small extent, neither of these companies offers a way to innovate its way to consistent growth. Both may have moments of strong growth spurts (and make no mistake, I much prefer PVH to Sony over the long term), but at these prices, short-sellers have every reason to be hovering like vultures.

What's your take on these three stocks? Do the short-sellers have these stocks pegged, or are they blowing smoke? Share your thoughts in the comments section below.

Fool contributor Sean Williams owns shares of Dell, but has no material interest in any other companies mentioned in this article. You can follow him on CAPS under the screen name TMFUltraLong, track every pick he makes under the screen name TrackUltraLong, and check him out on Twitter, where he goes by the handle @TMFUltraLong.

The Motley Fool owns shares of Best Buy, Staples, and Apple, and has short-sold shares of Sony. Motley Fool newsletter services have recommended buying shares of, and creating a bull call spread position in, Apple. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy that never needs to be sold short.