Yes, U.S. citizens who engage in banking in Switzerland should be taxed by the IRS. Moving money out of the country should have no bearing on whether or not the citizen in question should be taxed by the IRS. As an American citizen you have both a moral and legal obligation to pay your fair share in taxes, relative to your income, to support the infrastructure of our country. Moving and/or hiding your money in another country should not allow people to circumvent the IRS and not be taxed on that money.
Yes, people who use banks in Switzerland and other foreign countries should be subject to tax by the IRS. By using these offshore accounts, these individuals are trying to get around U.S. tax laws. The U.S. should implement systems to prevent people from using these loopholes as a way to take advantage of the system.
United States citizens who engage in banking in Switzerland generally are taxed by the IRS because they are United States citizens, so I am not sure what the question is directly referring to. I suppose there may be a loophole in terms of interest, which is something that should be addressed, if it is a problem. But don't assume banking in a different country exempts a person from tax.
No, U.S. citizens who engage in banking in Switzerland should not be taxed by the IRS, because they are not doing anything in the country. As far as the U.S. is concerned, that money does not exist. Someone who buys a blouse on vacation in France should not have to pay for sales tax back in the United States, either.
When a United States citizen goes to do his or her banking abroad, in a country like Switzerland, that man or woman should not be taxed for his or her financial activities. American financial institutions should recognize their limits and not attempt to over reach, especially when international monetary flows are involved.