Why should there be a limit? If you are able to sell some service or product that the public or a business is willing to pay for then you should be able to make as much money as the market and your talent to provide it can bear.
I don't think anyone should be over taxed, not even billionaires. I think they should be encouraged to invest in and expand their businesses and create more businesses as well. There is nothing wrong with profit. Why else do you work or start a business?
If someone making 50K/yr is taxed at 10% he pays $5,000 and if someone who makes 1 billion a year pays the same they pay 100 million. No matter what, that's one hell of a lot of money the government gets, why should he be punished for having success?
Bottom line is, I never got a job from a poor man or a poor business.
In America you should be able to rise as high and as far as your talent and ambition will take you.