The stock market finished out April on a strong note, with the S&P rising to a new all-time record high on optimism that earnings season is going well and that the economic recovery is proceeding at the perfect pace to encourage continued support from central banks around the world. The Dow Jones Industrials (DJINDICES:^DJI) fell just short of a new record of their own, but the average managed to add 21 points on the day.

But among the celebrations were some pockets of bad news. As I discussed earlier today, Pfizer was the biggest loser on the Dow, falling 4.5% after posting weaker-than-expected earnings. Consumer stocks Procter & Gamble (NYSE:PG) and Wal-Mart (NYSE:WMT) were also weak, however, with P&G losing more than 1% and Wal-Mart declining almost 1%. Barron's commentator Brendan Conway noted this morning that both Pfizer and Procter & Gamble are favorites among low-volatility ETFs, which have gained in popularity among risk-averse investors seeking protection from a possible future market decline. Wal-Mart is also a major holding in those ETFs, and as more investors have gravitated toward low-volatility stocks, their shares have gotten more expensively valued -- paradoxically leading them to have much more dangerous risk profiles than most investors recognize.

Beyond the Dow, Pitney Bowes (NYSE:PBI) plunged more than 15% after a disappointing earnings report that led the company to cut its dividend by 50%. Even though the stock will still yield more than 5%, the cut puts an end to Pitney Bowes' 30-year streak of annual dividend increases. Analysts had predicted for months that the dividend might need to be cut, but the company had foiled bearish investors for a long time before finally succumbing today.

Lastly, Nuance Communications (NASDAQ:NUAN) took an 18% haircut after the voice-recognition specialist reported weak sales and net income. Nuance, which is responsible for the Siri iPhone feature, isn't the first smartphone-related company to suffer from weakness in the industry, and today's report may add one more piece of evidence pointing to a larger-scale slowdown for smartphone sales as penetration rates start to approach saturation in many markets.

Fool contributor Dan Caplinger has no position in any stocks mentioned. You can follow him on Twitter: @DanCaplinger. The Motley Fool recommends Nuance Communications and Procter & Gamble and owns shares of Nuance Communications. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.