Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

Friday was a mixed day for the stock market, with major market benchmarks moving in different directions due to conflicting earnings news. Yet, even though the broadest stock market measures were down less than half a percent, big drops in shares of Silver Spring Networks (NYSE: SSNI), Elizabeth Arden (NASDAQ: RDEN), and SLM Corp. (SLM 0.24%) showed, once more, the willingness of investors to punish stocks that give disappointing news.

Silver Spring Networks plunged 25% after the maker of systems for smart-grid management issued poor preliminary fourth-quarter results last night. The company reduced its revenue-growth guidance to just 5% for the quarter, potentially causing Silver Spring to suffer an adjusted net loss for the quarter. Given that analysts were expecting a substantial profit on revenue growth closer to 25%, the news hit shareholders hard. Record backlog figures could help the company bounce back in the long run, but investors weren't willing to be patient today.

Elizabeth Arden dropped 19% after its preliminary holiday-quarter results pointed to a sharp shortfall in expectations. The company guided earnings to $1.05 to $1.08 per share, 27% to 29% below what investors were expecting from the company, with revenue of $415 million to $418 million falling more than 10% short of what investors had hoped to see. The company's decision not to respond to competitors' promotional discounting weighed on sales, with revenue in North America sinking 9% in the first half of the fiscal year. Arden also chose to pull its previous guidance for the full fiscal year, presumably because it expects not to meet those figures. The news gives another data point to anecdotal evidence of heavy discounting, and its impact on a variety of retail chains during the holidays.

Sallie Mae fell 10% after the student-loan company said last night that its fourth-quarter profit fell by 22%. The company fell well short of what investors had expected to see on the earnings front, but for long-term shareholders, the more interesting question is what impact its plan to split up its consumer-banking division from its educational-loan management business will have on its long-range earnings trends. The move could help Sallie Mae unlock value and better handle the changing regulatory environment in the financial industry.