Greg Mankiw points out high implicit marginal tax rates associated with health insurance reform as currently proposed. Insurance subsidies for low-income families phase out with income, meaning that as income rises, it is taxed away either implicitly through a reduction in health insurance subsidies or explicitly through payroll and income taxes.
The income levels he cites are not low: $54,000 for a family of four. The Earned Income Tax Credit also has a phaseout, but at a somewhat lower level of income, something like $35K - $40K or so.
