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 SanDisk Corporation (UNKNOWN:SNDK.DL) rallied 2% today after Bank of America upgraded the data-storage specialist from underperform to buy.

So what: Along with the two-notch upgrade, analyst Simon Dong-je Woo boosted his price target to $125 from $80, representing about 29% worth of upside to yesterday's close. While contrarian traders might be turned off by SanDisk's sharp climb during the past year, Dong-je Woo's call could reflect a sense on Wall Street that favorable industry trends give the stock plenty of room to run.

Now what: B of A raised its 2014 EPS view for SanDisk from $5.09 to $5.52 in 2014, from $4.95 to $6.74 in 2015, and from $4.73 to $7.52 in 2016. "Management's firm commitment to shareholder return (dividend/buyback using most of FCF) and mix improvement (more value-added products such as enterprise SSD) should warrant high multiples," said Dong-je Woo. "Low threat from competitors (chip supply constraint, disciplined capex) & new demand (China, B2B data storage, etc.) should lead to lower cyclical risk (WACC decrease) and more stable ASP (margin upside even at normal level of cost cut using new tech)." With SanDisk shares now up more than 85% from their 52-week lows, and trading at a P/E of 20, however, I'd hold out for a wider margin of safety before betting too heavily on that upbeat outlook.