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

What: Shares of Michael Kors (NYSE:KORS) climbed 2% in early Wednesday trading after Piper Jaffray upgraded the luxury retailer from neutral to overweight.

So what: Along with the upgrade, analyst Erinn Murphy boosted her price target on the stock to $90 (from $73), representing about 27% worth of upside to yesterday's close. Value investors might be turned off by the stock's hot run in 2013, but Murphy believes that there's plenty of room to run given the brand's rapid growth in popularity among teens.

Now what: According to Piper's "Taking Stock With Teens" survey, mindshare for Michael Kors' handbags are growing at a whopping rate and should translate overseas. "Europe will be the next catalyst in the model which will likely support a pathway approaching $6/share in earnings over time," Piper wrote in a note to clients. Of course, with the stock up more than 50% from its 52-week lows and trading at a P/E of 30, investors don't exactly have a wide margin of safety if Kors doesn't grow as Piper expects.

Fool contributor Brian Pacampara has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. 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.