The biggest risk for owning shares in the company you work for is often overlooked:
A single event, such as an economic downturn, can result in both a huge drop in the share price and job loss. So, at the time you might most need the money from the sale of the shares (or the dividend), might also co-incide with the company's share price drop. In other words, for whatever reason you get laid off might also be the reason the share price drops or dividend goes away.
Thus, owning shares for the company you work for can be very risky.