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.

In Motley Fool CAPS, more than 135,000 members have weighed in on nearly 5,300 stocks, sharing bullish and bearish opinions alike.

Consider Mac-king Apple (NASDAQ:AAPL). The stock has bucked the trend recently is actually up more than 60% year to date, but in Motley Fool CAPS, a significant number of the 21,919 members weighing in on the company still offer reasons to be bearish. I've already plucked out some of the common bullish rationale backing Apple today, so here are three counterpoints, courtesy of CAPS.

1. Stiff smartphone competition: Although the iPhone is incredibly popular, Research In Motion's (NASDAQ:RIMM) BlackBerry is still selling well, edging out the iPhone in market share gains in the first quarter. And the iPhone is constantly under attack from other contenders like Google's (NASDAQ:GOOG) Android and Palm's (NASDAQ:PALM) Pre, who are looking to steal market share too.

2. Falling Mac sales: iPhone sales have held up, but Mac sales have taken a hit just as more PCs from Hewlett-Packard (NYSE:HPQ) and Dell (NASDAQ:DELL) have been gathering dust on store shelves. Mac sales fell in the first quarter and research firm NPD Group saw a continued decline in May, with Mac unit sales dropping 3% year-over-year. With Macs making up a significant portion of Apple's revenue, the lack of growth there puts a damper on the iPhone enthusiasm for many investors.

3. Expensive shares: Shares have picked up huge gains since March and some CAPS members see little more short-term upside potential. An analyst from Canaccord Adams thinks things have moved a little too fast recently and downgraded Apple as recent Best Buy (NYSE:BBY) results show continued weakness in the retail environment.

Of course, Apple has successfully outmaneuvered dozens of obstacles in the past. But the question about whether the company will continue its great run is why CAPS is such a great resource to augment your own analysis.

To see what the very best CAPS members are saying now about Apple, just click on over to Motley Fool CAPS and have a look.

More Foolishness:

The Motley Fool Stock Advisor service still sees Apple poised to beat the market over the long haul -- despite the drawbacks. To see all the stocks that have helped Tom and David Gardner beat the market by 41 points on average, take a free 30-day trial.

Fool contributor Dave Mock did grow up pretty healthy and strong, but still contends that lima beans had nothing to do with it. He owns no shares of companies mentioned here. Google is a Rule Breakers selection. Apple and Best Buy are Stock Advisor recommendations. The Fool owns shares of Best Buy. The Fool's disclosure policy still hasn't figured out how to eat rice efficiently with chopsticks.