Gregory's Server
The argument of the mobility of extremely wealthy persons becomes less convincing, if you consider that e.g. Switzerland has a wealth tax and also, unlike e.g. Germany, taxes capital gains and income from financial and real estate speculation like other income, and yet, the ultra-rich are not leaving the country in hordes.
In fact, this form of taxation has led to overall lower taxes.
BTW: The famous banking secret in Switzerland is long gone.