It's a data leak involving tens of thousands of offshore bank accounts, naming dozens of prominent figures around the world. And new details are being released by the day — raising the prospect that accounts based on promises of secrecy and tax shelter could someday offer neither. Among those named include a top campaign official in France, the ex-wife of pardoned oil trader Marc Rich, Azerbaijan's ruling family, the daughter of Imelda Marcos and the late Baron Elie de Rothschild.