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 upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Netflix, (NASDAQ:NFLX) and Yelp Inc (NYSE:YELP) both rallied about 2% today after Oppenheimer upgraded the pair of tech plays from Neutral to Outperform.

So what: Along with the upgrade, analyst Jason Helfstein planted a price target of $419 on Netflix and $78 on Yelp, representing upside of 24% and 19%, respectively, to Friday's close. So while momentum traders might be turned off by the tech sector's weakness in recent weeks, Helfstein's call could reflect a growing sense on Wall Street that it's starting to offer some attractively priced opportunities.

Now what: According to Oppenheimer, both Netflix and Yelp have favorable near-term technical support. "In our view, the recent sell-off in high-beta Internet and technology stocks has created a buying opportunity in certain stocks in our coverage universe," said Helfstein. "As we view near-term fundamentals as unchanged, we are upgrading the shares of NFLX and YELP to Outperform from Perform." More important, with both Netflix and Yelp boasting a rock-solid balance sheet and attractive long-term growth prospects, the downside might be limited enough to buy into that bullishness.