On a tangential note, moving to Puerto Rico is one of the better ways for a US citizen who doesn't want to renounce to lawfully avoid federal capital gains taxes. Domiciling on a tropical island for a year to avoid 15% can be pretty attractive even for relatively modest equity gains.

Edit: Puerto Rico Act 22[1] is the law in question.

[1] https://en.wikipedia.org/wiki/Act_22_of_2012