Plug Power's stock price has collapsed more than 95% from its all-time highs, is this an opportunity to get in on the cheap or a sign of risk?Plug Power (PLUG -1.74%) isn't a penny stock, but it isn't far off, with a stock price hovering around $1.50 right now. Is it worth jumping in while the price is below$2 and over 95% below the all-time high price it hit around the turn of the century? There are exciting things happening with the business, but there are also things you need to be worried about.What do ...