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 SunEdison Inc (NASDAQOTH:SUNEQ) gained 3% in premarket trading Monday after Deutsche Bank upgraded the silicon wafer specialist from hold to buy.

So what: Along with the upgrade, analyst Vishal Shah boosted his price target to $35 (from $13), representing about 80% worth of upside to Friday's close. So while contrarian traders might be turned off by SunEdison's big price jump over the past year, Shah's call could reflect a sense on Wall Street that sector tailwinds give the stock plenty of room to run.

Now what: According to Deutsche, SunEdison's risk/reward trade-off is rather attractive at this point. "We are becoming increasingly constructive on the solar sector as we expect further tightening of the solar supply/demand balance and expect increased investor interest driving valuation multiple expansion," said Shah. "We expect the emergence of 5-6 publicly traded YieldCos over the next 12-18 months to act as a robust growth enabler as we expect a significant amount of low-cost capital to chase projects, driving improved project economics and greater amount of new project development." Of course, when you couple Sunedison's still-significant debt load with its red-hot and volatile stock price, I'd hold out for a much wider margin of safety before betting on it.