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 Zendesk, Inc. (NYSE:ZEN) popped 8% today after Canaccord Genuity initiated coverage on the software development specialist with a buy rating.

So what: Along with the bullish call, analyst Richard Davis planted a price target of $19 on the stock, representing about 23% worth of upside to Friday's close. So while conservative investors might be turned off by Zendesk's emerging nature, Davis' call could reflect a sense on Wall Street that its growth prospects are just too promising to pass on.

Now what: According to Canaccord, Zendesk's risk/reward trade-off is pretty attractive at this point. "Zendesk is a promising, albeit emerging firm that appears set to continue to rapidly win business with firms looking to deploy what we believe is a best-in- class customer engagement platform," said Davis. "Our $19 price target is based on an 8.8x EV/revenue multiple applied to our C2015 estimate of $161M, assuming roughly $55M in prospective net cash and a fully diluted post-deal share count of 77.3M." Given Zendesk's still-speculative business model and suddenly hot stock price, however, I'd wait for a much wider margin of safety before betting on those assumptions.