See this comment below. Also you could make the case that you are locking in the 15% LT cap gains rate, which could and likely will increase at some unknown point in the future.

>> The numbers on and analysis of his tax liability in the article are demonstrably wrong - at a level of error unworthy of The Economist. His tax liability is calculated on the value of the stock as of the date he renounces citizenship, which was last September. Today, Facebook is worth maybe $100 billion. Early this year, a private equity offering put the value at $50 billion. Last fall, who knows, and it's all subject to negotiation with the IRS - my guess is no more than $25 billion. That means he evades 75 % of the tax bite by renouncing citizenship, and will be paying at most maybe $125 to $150 million of that $500 to $600 million tax liability he would owe if he sold all his stock next week.