Effectively 'hiding' money offshore though opaque company ownership structures is possible when you have jurisdictions where even asking who owns the company could result in jail-time (see 5.1b of the Caymans confidential relationship law [1]). When you don't know who owns what, it becomes difficult to selectively 'turn people away'.

[1] http://www.cayman.gov.ky/pls/portal30/docs/FOLDER/SITE83/GAZ...