Per our multiple discussions here, it appears that not so long ago, the US already had heavily taxed the rich:

http://staff.jccc.edu/swilson/businessmath/fit.htm

The highest tax bracket taxed 90+% of income from WW2 to the 60s when it then dropped to 70% and then continued to drop from there.

I guess all the money just went to nukes, the interstates, the space program and public housing (ghettoisation).

Although, as the income tax rates dropped from 1950 - present, the payroll tax rate has increased from 3% to 15.3%, making the overall federal tax system even more regressive.

http://www.taxpolicycenter.org/TaxFacts/TFDB/TFTemplate.cfm?Docid=45&Topic2id=50