If the high tax rates only apply above $10 million, then the big impact would be on:

1. The most skilled global talent, who might choose to start their business elsewhere, where there would be the prospect of becoming super rich. 2. Angel investors and second-time founders. A major reason these founders would want to take risks, reinvest, and double down is to hit the home run, and have change-the-world amounts of money. 3. First-time founders who sell-out early to a big company, rather than try to go big. This could really do great damage to the pipeline of new and great products, since big companies are often where innovation goes to die.

I do agree that a high percent tax rate on income over $10 million would not do much to discourage run-of-the-mill new businesses, such as restaurants and landscaping companies. But I think it could majorly discourage the types of startups which drive the continued advancement of technology.