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 Las Vegas Sands (NYSE:LVS) sank 2% today after UBS downgraded the casino operator from buy to neutral.

So what: Along with the downgrade, analyst Robin Farley lowered his price target to $79 (from $88), representing about 8% worth of upside to yesterday's close. So while contrarian traders might be attracted to Las Vegas Sands' pullback in recent months, Farley's call could reflect a sense on Wall Street that unfavorable Far East trends will continue to pressure the stock.

Now what: According to UBS, Las Vegas Sands' risk/reward trade-off is pretty balanced at this point. "While much of investor concern has focused on UnionPay headlines out of Macau today and in recent weeks, we believe the real issue is slowing VIP end demand driven by macro trends in China," said Farley. "And while UnionPay regulatory changes are the kind of headline noise that can provide opportunity to buy on dips, we believe the unrelated slowdown in VIP growth is a bigger picture issue that could change the outlook for Macau growth and be an overhang on valuation." When you couple those risks with Las Vegas Sands' steep-ish 20-plus P/E, it's easy to understand UBS' cautiousness.