Second of all, it is wrong to bring an example of a chef in the context of the problem of disproportionally large reward of people who joined the company early compared to someone who joined the company later but contributed more.
Early joiners get paid for the risk. They acknowledge the risk before joining the startup and have a choice. Unfortunately chefs don't have a choice and in most cases they have to accept what they are being offered, because there is no other alternative.
Third of all, paying $20M a chef can be treated as an extremely successful public relations move. This helped Google to gain that image of the "don't be evil" Robin Hood operating on the Land Of Opportunities. On the other side, rich Zynga executives paint themselves in evil tones when denying money from a poor chef.
The real question is what should be encouraged more: risk taking or professionalism. Zynga executives believe the later. Which probably reflects the fact startups are becoming more like corporations.
But this is a first world problem and has nothing to do with the poor chef who was lucky enough to win a lottery in form of Google.