Momentum investors love to back companies with the wind in their sails. Contrarian investors typically pick up the cigar butts the market has tossed aside. So what do you call investors who turn against winners? Sourpusses? Shorts?

Over on Motley Fool CAPS, we sometimes call them the savviest investors around. When one of our All-Stars -- those whose stock-picking prowess places them in at least the 80th percentile of our community -- sours on a top-rated stock, perhaps we should take notice. Perhaps the member's found a chink in that highflier's armor, or a question mark in its financial footnotes. Or maybe it's just a hunch. That's why these tables aren't lists of stocks to buy or sell -- just starting points for further research.

Here's a list of stocks that some All-Stars have spurned recently:

Company

CAPS Rating (Out of 5 Max)

Est. Long-Term EPS Growth

CAPS All-Star

Player Rating

DXP Enterprises (NASDAQ:DXPE)

****

20%

TMFBreakerBrian

99.71

NYSE Euronext (NYSE:NYX)

*****

21%

BagToter

98.83

Amgen (NASDAQ:AMGN)

****

10%

VINY17

93.57

Robbins & Myers (NYSE:RBN)

*****

15%

naylorj

92.22

Atheros Communications (NASDAQ:ATHR)

*****

20%

JC4Fund

91.05

Source: Yahoo! Finance; Motley Fool CAPS.

Considering that on average, 95% of investors rating these companies think they will outperform the market, what might have turned some of CAPS' top members against them?

No anemic results
As some Foolish analysts have noted, beyond Amgen's osteoporosis drug denosumab, the pipeline of candidates is pretty much a roll of the dice. Yet it seems that will be enough, because late-stage study results met the company's goal of reducing vertebrae fractures in postmenopausal women. Amgen's stock got a further boost when sales of several drugs, including Aranesp and Epogen, came in ahead of analyst estimates. And the company raised both revenue and EPS guidance for the full year, pleasing many.

CAPS member kahunacfa finds that Amgen is undervalued.

Amgen(AMGN) is a large, successful [biotech] that uses its science to discover and develop advanced agents for the improvement of Human Health. By my estimate, I expect the company to [be able] to grow earnings in the 9.5% to 10.5% [range] over the next ten years or so. Using my Intrinsic Value Model, the company's Intrinsic Value is in the $94 to $98 range.

Pump up the volume
Not only are listings on the stock exchanges a competitive model, but encouraging higher trading volumes is one as well. NYSE Euronext has been playing the game sharply with international exposure to a number of markets. In June, trading volume on its European exchanges increased nearly 13%, along with an 8.5% increase here at home, while almost 200 new listings were added overall. NASDAQ OMX Group (NASDAQ:NDAQ) hasn't been idle, either, with a 43% increase in volume last month. For June, volume fell for commodities exchange operator CME Group (NASDAQ:CME), though it was up for the full second quarter.

Early last month, top-rated CAPS member ChazzReinhold saw NYSE Euronext, a Motley Fool Rule Breakers recommendation, trading at some of its lowest prices ever, but also saw a number of initiatives.

Pushing [its] 52-Week lows... NYSE increasing market share in the option business, ETF listings, closed-end funds and structured products trading...Imagine a future where dozens of developing countries become more prevalent in the equity markets and NYSE could be a one-stop shop where investors can buy global stocks, futures, options, exchange-traded funds, and bonds. It could challenge the powerhouse futures markets and, with a new place for hot young companies to list, could steal much of the thunder of U.S. rival NASDAQ. It could even own a European exchange. Will this happen? Why not?

Make lemonade from lemons
We've seen the direction some investors have indicated they believe these companies are heading, but Motley Fool CAPS is more than what they think, even if they're All-Stars. It's where we invite you to share your thoughts and insights and add your voice to the debate. Go ahead, have your say. We're eagerly waiting!

Atheros Communications is a Motley Fool Hidden Gems selection. NASDAQ OMX Group is an Inside Value pick. Try any of our Foolish newsletters today, free for 30 days.

Fool contributor Rich Duprey does not have a financial position in any of the stocks mentioned in this article. You can see his holdings. The Motley Fool has a disclosure policy.