There's a first rate article on flat tax in a Czech publication called TOL today. Adam Cardais says:
Karl Marx might be shocked to see who's doing what with tax systems in Central and Eastern Europe these days.
After all, it's the capitalist West that won't abandon progressive tax systems, which Marx championed in The Communist Manifesto, while the former Soviet bloc countries are lining up to buck their old ideological fountainhead by moving to a more regressive structure: a single tax rate for nearly all earners, regardless of income.
It's well worth a read. In particular I like this:
If, then, the flat tax is often nothing more than tax cuts in fancy dress, the resulting drop in revenues raises serious questions about how long governments can afford to embrace it.
A good question.