When Ben Bernanke speaks, the markets listens, and today he said the Federal Reserve will be flexible in its bond-buying programs and respond to data as it comes in. This isn't really new news if you've listened to Bernanke over the past six months, but some like to parse every word he says, injecting fear or greed into the market on a day-to-day basis. But here's the bottom line: Bernanke and Co. aren't going to pull the training wheels off the economic bicycle until they know it can ride on its own. Today, the market saw Bernanke's comments as reassuring and pushed the S&P 500 (SNPINDEX:^GSPC) up 0.21% late in trading, while the Dow Jones Industrial Average (DJINDICES:^DJI) lagged with a 0..4% gain because of a few big losers.

The biggest loser on the Dow is American Express (NYSE:AXP), which has dropped 1.9% today. The European Commission is planning to cap the transaction fees banks charge retailers at 0.2% for debit cards and 0.3% for credit cards. This is still only draft legislation, but it would hit American Express' bottom line if nothing were done to offset it. The U.S. has also made efforts to cap the charges card companies can demand of retailers. American Express and the rest of the industry will adapt, likely with little long-term profit change. 

Another Dow stock sinking is Caterpillar (NYSE:CAT), also down 1.9% after it was put on notice by short-seller James S. Chanos, who said he was shorting the stock because Caterpillar faces a lot of headwinds relating to the commodities market, where miners generate demand. If commodities demand drops in China, it will hit Caterpillar's sales and profit. The stock still pays a considerable 2.8% dividend yield and trades at just 12 times trailing earnings, but demand can swing wildly, and eventually China will have to stop its stimulus-fueled growth, which could have a big impact on demand. A short-seller's call isn't reason to dump the stock, but it may be a reminder to look at the macro picture and re-evaluate Caterpillar's prospects.  

DuPont (NYSE:DD) is up a whopping 4.7% today after Nelson Peltz's Train Fund Management revealed a large stake in the company. The stock hasn't exactly been a barn-burner recently, leading the Dow by about 3% so far in 2013. And Peltz didn't have much comment, but investors quickly bid up shares to follow his lead. Following big-name hedge funds isn't a good idea, so do your own due diligence on a stock like DuPont before following Peltz's lead.