I don't doubt that most of them worked very hard and took a lot of risks to get where they are now. I respect these people immensely. But no human could work hard enough or provides enough of a service that they deserve to earn tens of thousands of times more than the people who actually do the labor.

Bardeen co-invented the transistor and the theory of superconductivity, yet even though his work was recognized with two Nobels, he didn't die a billionaire. Zuckerberg made a social network barely different from the others, but because he was able to market it better, or was just at the right time at the right place, he's now a billionaire. I respect Zuckerberg, but if he is able to earn 35e9 USD and Bardeen isn't, even though both did what they loved, the system is broken.