Friday gave stock market investors some respite from losses earlier in the week, as major-market benchmarks managed to recover by around a quarter of a percent. Merger and acquisition activity helped bolster stocks in many different parts of the market, but concerns about the sustainability of the economic recovery held others back. Finisar (NASDAQ:FNSR), InterDigital (NASDAQ:IDCC), and GNC Holdings (NYSE:GNC) were among the worst performers of the day.

Source: Finisar.

Finisar plummeted 22% after the maker of fiber-optic network components reported subpar fiscal fourth-quarter results, and gave gloomy guidance for the current quarter, as well. Even though sales jumped by more than a quarter, a plunge of more than four full percentage points in gross margin weighed on overall profitability. Finisar remains upbeat about its achievements, with hopes to keep its market share rising, and to make the most of an upsurge in capital spending among telecom-company customers. The question is whether shareholders will be willing to turn what had been a growth-stock play into a value proposition now that shares have been beaten down so far.

InterDigital lost 7% after a judge ruled that Nokia (NYSE:NOK) and China's ZTE had not infringed on wireless-transmission technology patented by InterDigital. InterDigital CEO William Merritt issued a statement after the decision, disagreeing with the decision, but suggesting that an appeal to federal appellate court might yield a better result in the long run. InterDigital has generally been successful in getting many companies to license its technology, with an agreement last week with Samsung having led InterDigital to revise its second-quarter revenue guidance upward. Still, with the stock trading at lofty heights, InterDigital needs all the revenue it can get to justify its valuation.

Source: GNC.

GNC Holdings fell 6% in the wake of the resignation of its chief financial officer. Michael Nuzzo will take a job at a private company in the consumer-products industry, giving about five weeks' notice in order to help GNC meet its obligations to report its second-quarter financials. GNC stock has been under pressure all year, with the company's first-quarter results showing disappointingly slow growth of just 0.7% in same-store sales. Falling gross margins accompanied weather-related impacts, but increased competition from nutritional-product selling rivals has also weighed on investor sentiment. Until GNC finds a way to distinguish itself, it could be tough for its stock to get back on track.