Financial advisers are starting to refer to their wealthiest clients as billionaire nomads -- those who globe-trot between homes to avoid direct taxes from any country.

Ultra-high net worth families have always been mobile, but the crackdown on offshore accounts is making them even more so. A few have even taken to living on megayachts, apparently deciding that pirates on the high seas are less of a risk than dodging the remorseless embrace of tax authorities.