While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Qualcomm (NASDAQ:QCOM) fell 2% today after Piper Jaffray downgraded the mobile chipset giant from overweight to neutral.

So what: Along with the downgrade, analyst Auguste Gus Richard lowered his price target on the stock to $67 per share (from $71), representing about 3% worth of downside to yesterday's close. The stock has been on a nice run in recent months, but Richard's recent channel checks with foundry contacts (revealing production slowdowns), coupled with intensifying low-end foreign competition, suggest that Qualcomm is facing some headwinds that Wall Street is overlooking.

Now what: Richard doesn't expect the trend toward emerging markets sales to slow anytime soon. "MediaTek, the low-end Chinese OEM supplier, announced unit cell phone chipset shipments that were up 49% Q/Q and guided units up roughly 20% Q/Q," Richard cautioned Qualcomm investors. "We believe these datapoints point to an accelerating mix shift to the low-end that we believe will impact QCOM's royalty stream. Our below-consensus FY14 estimates anticipate this shift." Given Qualcomm's still-dominant competitive position, fortress-like balance sheet, and 2% dividend yield, however, I'd wait for more evidence of that trend before selling too big of a stake. 

Fool contributor Brian Pacampara has no position in any stocks mentioned. The Motley Fool owns shares of Qualcomm. Try any of our Foolish newsletter services free for 30 days. 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 Motley Fool has a disclosure policy.