I'm not an expert on this, but when you exercise stock options you have to pay taxes on the fair market value at that time. In some cases it might make sense t

I'm not an expert on this, but when you exercise stock options you have to pay taxes on the fair market value at that time. In some cases it might make sense to exercise stock options before you can actually sell them (e.g. if you expect the price to keep going up to save on taxes or if you're leaving the company when you typically only have a limited amount of time to exercise or lose those options). So in these cases you now own the stock and paid taxes on it, but if the stock price falls drastically after that you might have actually paid more taxes than the stock is worth now.