That would require intent to be proven.
(Not impossible or unfalsifiable, but it's another hurdle)
>Additionally, a judge could put you in prison indefinitely until you disclose and transfer your bitcoins.
If a third party spends those coins because they have the wallet file, the other copy of the wallet file becomes worthless and is no longer in your control to do anything with.
>Finally, the public paper trail of bitcoins will make it hard to "hide" them.
Not really. Between tumbling services, and the fact that it's stupidly easy to create a wallet out of thin air, at that point you've broken the ownership chain. (If wallet 123, known to belong to me, sends coins to wallet 456, you can't prove whether wallet 456 is under my control unless you happen upon the file in my possession).
One statistic points to $500 million forfeited in 2010. That was a doubling since 2002, and something that did not even exist roughly 40 years ago.
http://online.wsj.com/article/SB1000142405311190348090457651...
There are many different US government agencies that can seize your assets, without trial, for a large number of reasons. This is not limited to you drugs or organized crime, but rather someone's belief that your money came from something that was illegal. In a case going to the Supreme Court next week, what they are being charged with may not even be illegal. The WSJ appropriately titles the article "How Prosecutors Rig Trials by Freezing Assets."
http://online.wsj.com/article/SB1000142412788732411040457863...
Unfortunately bitcoin is not the solution. Because, if you attempt to use it to prevent asset forfeiture now your breaking money laundering laws. So now you can end up in jail even if you never did anything wrong in the first place.
Additionally, a judge could put you in prison indefinitely until you disclose and transfer your bitcoins. Unless you are facing the death penalty, and have a whole lot of bitcoins, you probably don't have much leverage.
Finally, the public paper trail of bitcoins will make it hard to "hide" them. I'm going to guess some of these regulators are split between liking and hating them. I would imagine that they are already piecing together the puzzle based on subpoenaed data and what is better sent to them from US compliant exchanges.
What is the solution? Making people aware that they are not free. That anyone in the state, local, or federal government has the ability to seize all of their assets at anytime. Making sure they understand that if this happens, they better have friends who will graciously front them hundreds of thousands or millions of dollars or else they will be seeing a public defender.