Plug Power (PLUG -1.70%) stock was having a banner week, at least through Thursday. The stock had soared by more than 20% heading into the company's fourth-quarter earnings report Friday morning. But shares plunged after the market got a look at that report. Still, as of late Friday morning, Plug Power stock was trading about 6% higher than where it started the week, according to data provided by S&P Global Market Intelligence. There was some good news in the company's earnings report, but investors still d ...