Unlike most countries in the world, the United States taxes its citizens that live abroad. Take for example, John T. Citizen. If Mr. Citizen were to move to the United Kingdom, he would pay the UK’s income tax plus the US’s income tax. To give the American government some credit, they do allow a certain amount of income to be credited (up to $90 something thousand) but that is chump change to people like Mr. Saverin. So if you’re a high end earner paying one country say, 40% and then the US another 35%, I can see why you’d want to consider renouncing citizenship and cutting of the IRS.
I have thought though about meeting a Canadian or a Brit and maybe falling in love with that guy. I would emigrate for love. I’d prefer to stay but given the absurd state of gay rights in this country I’d leave. I don’t think that makes me a traitor because I can find happiness elsewhere. So what if I did find that special guy, would I become a British or Canadian citizen? I’m honestly torn but I would lean to yes.