[bjterry]

It's not that naive. When considering your investments, you should consider your employment as part of your investment capital (in investment management this is your "human capital"). It's important to realize that your salary is more like a bond than an equity, but once you've taken that into account the author's thesis is basically correct. You are taking additional risk by investing your financial capital and human capital in the same asset.

It's far more naive to keep your entire investment in your employer than to sell all of it and diversify, even if neither of those is necessarily optimal. It's extremely naive to think that you have special insight into the future returns of a multi-billion dollar publicly traded company when you are a developer one year out of college, just because you work there.