After two straight days of big gains, the S&P 500 Index (^GSPC 0.02%) sold off big-time Wednesday, dropping 22 points, or 1.4%, to end the day at 1,628. Wall Street turned bearish on a dime in afternoon trading as Fed Chairman Ben Bernanke signaled a slowdown in the central bank's quantitative easing efforts, given continued economic growth. That's right -- stocks sold off when Bernanke expressed his bullish outlook on the American economy. More than 75% of publicly traded shares fell Wednesday, but three of them stood out as some of the biggest losers of the day.

Regeneron Pharmaceuticals (REGN -0.09%), which was one of yesterday's 3 Best Stocks, slipped 4.7%, giving up all of Tuesday's gains and a little bit more. Today's slip may just be a reflection of investors' taking their gains from yesterday's surge, but it could also signal the exit of some longer-term investors spooked by the Fed's comments today. Though it's often not a good idea, people often sell off the winners in their portfolio first, holding on to the losers in hopes for a comeback. And most longer-term investors in Regeneron are winners -- the stock's up nearly 850% in the past three years alone. 

Plum Creek Timber (PCL.DL), which is a real estate investment trust, or REIT, also lost 4.7% today. REITs had a rough go of it Wednesday; they frequently borrow money to pay their high dividends, and with the prospect of higher interest rates around the corner as the Fed starts allowing rates to rise, REITs like Plum Creek will have to pay more just to keep their payouts stagnant.

Lastly, shares of telecom giant Sprint Nextel (S) plummeted 4.4% as DISH Network declined to continue a bidding war with Japan-run SoftBank to acquire Sprint. As a Sprint shareholder, when other companies have a bidding war to acquire your stock, you tend to enjoy the process and rue the day when the bidding ends. SoftBank's offer, $21.6 billion, is only slightly above the current market value of Sprint's stock, which sits at $21.1 billion.