Oh, no.
One person can't buy a billion dollar company.
I don't see a problem with that and as I said Id use the money for the benefit of the nation as a whole.
One person can't or can buy a company? If you meant "can," what about a $2b company?
What would happen to the stock market if wealth were limited to $1b? Companies wanting to go public would see more small investors and fewer big investors. If you had an idea that required a $1b investment, you won't find a lone investor to back your business plan. If you happen to find two, and each invested their entire net worth, at $500,000 each, their return is limited to $500,000. The company would then be worth $2b, the owners will sell their stock, and presumably, exit the capital sector as the wealth limit has been reached.
Then the cycle starts all over again. If the company continues to grow, shareholders sell and drop out as the $1b limit is reached. This would obviously prohibit multi-billionaires, but it would seem to do nothing to stop the accumulation of wealth by capitalist speculators.
This of course assumes conditions remain the same, which they definitely would not. Limiting wealth to $1b would have drastic negative effects on the economy.
The responsibility for growth would be taken from the individual and given to collective investment. The larger the company, the greater the coalition needed for a controlling interest. Amazon, with a market cap of $222b, could be owned by no fewer than 222 individuals. The person who created and built the company, would by law, be limited to having the same control over his company as 221 other individuals. The incentive to start and grow a company is greatly diminished with a wealth cap.
Push-button economics doesn't work. Economic behavior doesn't rely on data. Data reveals the behavior. Thinking we can "end hunger" by limiting wealth is a knee-jerk emotional response. It's not well thought out.
There are two competing interests here. Business and labor. The old-fashioned method of unionization still works best. Limiting wealth to $1b won't get anyone a raise. Limiting billionaires' cash flow by going on strike will.