Norfolk Southern (NYSE: NSC) dropped more than 7%, while CSX (NASDAQ: CSX) experienced a 6% decline. Investors are nervous about a whole host of issues, ranging from the pace of the economic recovery and the future path of interest rates and inflation to current valuations of the market in general and high-growth stocks in particular. On Thursday, railroad stocks found themselves in the crosshairs of bearish sentiment, and it's unclear whether the drop will prove to be a bargain opportunity or just the beginning of a more extensive move lower for the companies.