A shell-shocked economy, spiraling debt at financial institutions, or just plain bad management -- on any given day, investors can name a number of reasons to sell a stock. Yet while panic never helps investors, it's still a good idea to play devil's advocate with investments from time to time.

Consider athleticwear and footwear designer Under Armour (NYSE:UA). The company has shown solid performance lately, but in Motley Fool CAPS, a significant number of the 2,510 members weighing in on the company offer reasons to be bearish. I've already plucked out some of the common bullish rationale backing Under Armour today, so here are three counterpoints, courtesy of CAPS.

1. Uncertain macro environment
The current environment is still tough on clothing brands such as Volcom (NASDAQ:VLCM), and even Under Armour is peering into a cloudy future in the near term. Some investors aren't swayed enough by the valuation of Under Armour shares to buy them today, based on current estimates of growth and a price-to-earnings ratio of 27. 

2. Weak sales
The economy isn't playing favorites. Consumers' spending cutbacks are wreaking havoc on premium retailers such as Abercrombie & Fitch (NYSE:ANF) and discounters such as Target (NYSE:TGT) alike. Under Armour posted weak sales numbers last quarter, plagued by order cancellations and lower-than-anticipated orders. Like many other retailers, Under Armour can't say that the weak market will rebound any time soon, leading some investors to believe that the top line could get even worse.

3. Growing costs
Under Amour's profit margins have lagged those of rivals Deckers Outdoor (NASDAQ:DECK), Nike (NYSE:NKE), and Columbia Sportswear (NASDAQ:COLM) in the last four quarters. While the company has managed to gain control of its rising inventories, investors haven't been too pleased lately with rising costs that have outpaced sales. In the fourth quarter, Under Armour's selling, general, and administrative (SG&A) expenses were up 9%, while sales ticked up only 2.5%.

Of course, Under Armour has weathered storms in the past. Can it successfully navigate the current turmoil? The uncertainty surrounding the company makes CAPS a great resource to augment your own analysis.

To see what the very best CAPS members are saying now about Under Armour, just click on over to Motley Fool CAPS and have a look -- it's all free, and even open to your opinion.

More Foolishness:

Under Armour is one of dozens of stocks selected by the Motley Fool Rule Breakers service to beat the market over the long haul. To see all the stocks David Gardner and the analyst team have recommended, take a free 30-day trial today.

Fool contributor Dave Mock usually takes about three tries before he hits a free throw. He owns no shares of companies mentioned here. Under Armour is a Rule Breakers recommendation. Columbia Sportswear, Under Armour, and Volcom are Motley Fool Hidden Gems recommendations. The Fool owns shares of Under Armour. The Fool's disclosure policy can hit a bottle cap from 50 yards with its Red Ryder BB gun.