In the world of ugly hypotheticals, I now bring to your attention the next attack by Team America World Police: we are all crooks.
Because all bitcoin transactions are known and public every bitcoin will eventually pass through "criminal hands" and this will be, to an extent detectable.
For example, let's say drug lord "50-btcs" transfers around some of his millions in bitcoins. The FBI, by tracing sales of bitcoins for cash or by seizing the guy's harddrive or whatever, identifies transactions involving those bitcoins. Well, now according to the United Police States of America those are "proceeds of criminal activity", so the unlucky current holder of those bitcoins could be getting free trip to one of our spanking new supermax Federal concentration camps.
Of course, this happens currently with plain old cash. Pretty much every 100-dollar bill you ever had passed through some drug dealer's hands at some point, the only difference was that nobody could prove it in a court of law.
Now, with bitcoins, they can and they will (maybe?)
