There's also the fact that owning stock of the company you work for / are the CEO of puts you at double the risk. If the company goes poorly, you're a lot more

There's also the fact that owning stock of the company you work for / are the CEO of puts you at double the risk. If the company goes poorly, you're a lot more likely to get laid off / ousted. If this happens, you might want to tap into your investments, but if the company does poorly, your investments are suddenly worth a lot less. If you diversify and invest in a wide array of companies, you're a lot less exposed to the risks of catastrophic changes in your industry.