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 Waste Management (NYSE:WM) slipped nearly 1% in premarket trading today after Wunderlich Securities downgraded the waste management company from buy to hold.

So what: Along with the downgrade, analyst Michael Hoffman lowered his price target to $45 (from $52), representing about 8% worth of upside to yesterday's close. While contrarians might be attracted to Waste Management's earnings-related pullback yesterday, Hoffman thinks that its appreciation potential remains limited given the relatively poor performance of its waste to energy and recycling segments.

Now what: According to Wunderlich, Waste Management's risk/reward trade-off is pretty balanced at this point. "WTE and Recycling remain margin and FCF drags: They actually underperformed expectations in 2013 and are not expected to be better than flat y/y in 2014," noted Hoffman. "Recycling is in a multi-year change in the operating model and WTE does not need to be owned 100% by WM for it to get the strategic advantage of disposal." With the stock now off more than 10% from its 52-week highs and boasting a 3%-plus dividend yield, however, those short-term concerns might provide patient Fools with a juicy long-term income opportunity.