The idea gaining popularity among European politicians. An Austrian member of the European Parliament, Jörg Leichtfried, favors the plan for forced loans, saying the rich could lend to the states at low interest rates. The loans, he said, would not be an “expropriation,” since they would be paid back. The head of Austria’s Social Democratic Group also backs the plan, saying states need to fix their budget troubles.

Yet others are opposed. Austria’s Finance Minister said the plan would chase the wealthy to other countries. France is already seeing a flight of the millionaires ahead of its plan to impose a 75 percent top tax rate on those making more than a million euros a year.

There is also a problem with the logistics of any wealth tax. Determining people's real earnings has proven hard enough for tax officials in Europe. Determing the value of their assets and wealth — from homes and private business to art and boats — is even harder.

Still, the combined issues of inequality and fiscal crises are likely to lead to more calls for the rich to bail out governments.

Do you think think the “forced loan” program would work in Europe?

-By CNBC's Robert FrankFollow Robert Frank on Twitter: @robtfrank

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