Data havens and strong cryptography have long been the bedrock of anonymous and untraceable digital currency transactions and their associated services. James Grimmelmann has published an excellent account of the entire Sealand and HavenCo saga entitled "Sealand, HavenCo, and the Rule of Law".
You can also read James' recent blog entries:
"Sealand and HavenCo Part I: The History of Sealand" (February 14, 2011);
"Sealand and HavenCo Part II: The Rise and Fall of HavenCo" (February 15, 2011).
For further viewing:
"Sealand The Mystery Solved - Part One"
"Sealand The Mystery Solved - Part Two"
"Sealand The Mystery Solved - Part Three"
"Sealand The Mystery Solved - Part Four"
"Sealand on Bravo Channel 2001"
"Sealand on the UK Evening News Sept 2002"
"Life in Sealand after the Fire"
"Sealand for Sale, an Interview with Prince Michael"