Yet some local experts doubt the new disclosure rule will cause a massive outflow of cash from South Florida. Few banking systems are as secure as that of the U.S.

Plus, the trend toward increased transparency isn’t limited to U.S. banks. Governments around the world are starting to crack down on tax evasion, which is responsible for up to $280 billion in uncollected income tax globally, according to a report from the Tax Justice Network.

“The effect of this regulation may not be as onerous as some people unfortunately fear,” said Miami-based banking lawyer Bowman Brown. Foreign depositors are “looking at the same thing world wide,” he said, so even those who who want to take their money out of the U.S. may have few alternatives.

Defenders of the new regulation say it’s a necessary gesture so the IRS can access information on accounts held by American nationals in other countries.

“The IRS is not just doing something because they want to penalize banks. They don’t want to waste their time and resources saying that the bankers are the bad guys,” said Ken Thomas, an economist and Miami banking expert. “They must believe that there’s a significant amount of lost revenue to pass something as controversial as this. The banking lobby is very strong.”

Bill Sharp, a tax lawyer with offices in Tampa, San Francisco and Zurich, has been watching what he calls the “mega-trend of global compliance” unfold for more than two decades, beginning in the late 1980s with a trickle of voluntary disclosure campaigns allowing Americans to declare offshore wealth without facing penalties. When authorities started cracking down on funding for terrorism after September 11, 2011, they also uncovered rampant tax evasion that had long gone unchecked.

A major shift came in February of 2009, when the U.S. Department of Justice reached an agreement with the Swiss government that breached the famous secrecy of Swiss banks. The catalyst was a federal case against banking giant UBS that alleged, among other things, that UBS bankers courted wealthy clients at Art Basel Miami Beach, pitching ideas for offshore accounts. UBS entered into a deferred prosecution agreement, agreeing to pay a $780 million penalty and to disclose information on hundreds of U.S. taxpayers who had accounts with the Zurich-based bank.

The IRS saw this case as “the poster child for why we need to attack bank secrecy,” said Sharp, not just for the penalty collected, but also for the thousands of Americans who voluntarily came forward to confess their offshore tax transgressions.

Critics of this recent IRS rule argue that while the new standard of transparency makes sense for countries in Europe and the Caribbean that harbor hidden accounts, few Americans keep their money in Pakistan or Portugal. In total, almost 80 countries are included on the list of countries with which the IRS has promised to share information.

“What American has a banking account in Peru? In Chavez’s Venezuela?” asked Alex Sanchez, president and CEO of the Florida Bankers Association and an outspoken critic of the regulation. “You know what is the No. 1 extortion and kidnapping country in the world? Mexico. What American is going to keep their money there?”

Those dangers are one reason international clients want their finances to remain private. The regulation does include a clause that gives the IRS the option of withholding// financial information in certain situations, but Miami bankers say that this vague promise is not enough to reassure clients. worried about their financial privacy and physical safety.