There's a more concrete, specific reason, than generic risk that you should consider and discount the stock price of the company you work for accordingly: it is less liquid for you relative to the market, because you cannot trade it in blackout periods. Lack of liquidity is a cost to you, therefore, if you work at Google, a share of GOOG should be less valuable to you than the market price (assuming you consider the current market price to be fair, which is a totally different matter).