From an excellent post by John C. Goodman:
After John Templeton renounced his citizenship and moved to Nassau where there is no income tax, the federal government imposed penalties — to discourage other wealthy people from doing the same thing. That was because the government wants to tax them. But when a wealthy person expatriates, the distribution of income and wealth becomes more equal. Should we reverse course and encourage the John Templetons of this world to get out of town. If equality is a serious goal, we should at least relax the penalties.