[twblalock]

There are several arguments against it:

If you depend on a small number of people for the majority of tax revenue, you will end up with unstable revenue. Look what happened to California's tax revenue during the 2008 recession. It dropped because the small number of rich people who pay more than half of the taxes got hit pretty hard by the recession.

Besides, do we really want to live in a society where only a small group of people has a financial stake in the funding of the government? Voters would probably be a bit more informed if they had some skin in the game. We really don't want to live in a society where the majority of voters will always approve spending increases because they know their taxes won't increase, and the cost of the increase will be borne by the top few percent. That will get us a runaway train of government spending.