There are three possible outcomes for startups: (1) failure; (2) marginally successful; and (3) enormously successful. In case of (1) and (2) employees hardly make any money, and early employees may make money in case (3). More than 99% startups' outcome is either (1) or (2).

I feel startup world is highly skewed in favor of investors and founders. I have worked at a startup and now I would think twice before working for another startup, since rewards don't add up to effort and time because of odds.