Let this possibly be a lesson. Use encryption. If you're on a mac, go, right now, and tick the FileVault checkbox. Windows users go download TrueCrypt and turn on whole-disc encryption. The law in this country is so complicated that, increasingly, it doesn't matter if you've broken the law or not. I don't side with Gawker. But I do know that if you have years of browsing history lying around, surely there's something…
You may want to read up on U.S. v Boucher, 2009. Unless you're hiding evidence of something particularly heinous, refusing to provide a means of decryption may land you in more trouble than the crime of which you're suspected.
Either way, the Constitution is clear on this issue: "no person ... shall be compelled in any criminal case to be a witness against himself". If a safe is found in your house, the government can do whatever they want to open it. They can blow it up, or they can ask your friends for the combination, or even just try every combination. But they can't punish you for not giving them the combination.
Cryptography is a very strong safe.
(A quick reading of related cases leads me to believe that this one is more relevant: http://supreme.justia.com/us/487/201/case.html. It holds that "In order to be "testimonial," an accused's oral or written communication, or act, must itself, explicitly or implicitly, relate a factual assertion or disclose information." Since reveling the decryption key is a factual assertion and discloses information, it is protected. Note that in Boucher, it is not clear that the key would disclose information.
But honestly, I think my Google skills are just better than the Appeals court in that case. I doubt that the decision would hold up in the Supreme court. And I especially doubt that one could be compelled to give up his or her key in normal, non-customs, criminal proceedings. IANAL.)