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 ExxonMobil Corporation (NYSE:XOM) slipped nearly 1% this morning after Bank of America downgraded the oil giant from neutral to buy.

So what: Along with the downgrade, B of A lowered its price target to $106 (from $110), representing about 7% worth of upside to yesterday's close. While momentum traders might be attracted to the stock's strong run in recent months, B of A believes that headwinds outside of Exxon's control -- production cuts announced by the Dutch government and a looming lease expiry in the UAE -- will likely weigh on production in 2014.

Now what: According to B of A, Exxon's risk/reward trade-off is pretty balanced at this point. "A series of recent announcements outside XOM's control risks cancelling out prod'n growth in 2014," noted B of A. "The combined loss of ~190,000 boepd essentially wipes out planned growth of ~4% in 2014; while the impact on earnings is modest, reassessing XOM's broader portfolio leads us to raise the issue of a potentially higher Gov't take at its flagship RasGas development as consequence of higher oil prices in recent years." When you couple Exxon's operating headwinds with the stock's strength of late, taking some money off the table certainly seems like a prudent move.