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 Facebook (NASDAQ:FB) closed down 1% yesterday after Raymond James downgraded the social networking giant from strong buy to outperform.

So what: Despite the downgrade, analyst Aaron Kessler boosted his price target on the stock to $56 (from $38), representing about 11% worth of upside to where it sits now. Facebook has skyrocketed over the past three months on better-than-expected advertising revenue, but Kessler believes that the current valuation leaves investors with little room for outsized gains going forward.

Now what: While Raymond James sees limited upside for the stock, it remains bullish on Facebook's growth prospects. "Our $56 price target (up from $38) is based on 19x our new 2015 EBITDA estimate," noted Raymond James. "We maintain our positive fundamental view on Facebook and expect 3Q upside driven by strong traction with mobile advertising (estimate 23% q/q growth) as well as newer ad formats (i.e., Mobile App Install, Page Post Link ads), though would note the much more positive investor sentiment and heightened expectations going into 3Q (vs. negative sentiment ahead of 2Q)." With Facebook shares having doubled over the past three months alone and currently trading at a forward P/E of 55, conservative investors would probably do well to heed Raymond James' words of caution.

Fool contributor Brian Pacampara has no position in any stocks mentioned. The Motley Fool recommends Facebook. The Motley Fool owns shares of Facebook. 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.