Actually Bitcoin is being used in all types of illegal ways, First they run it thru a mixer, or multiple wallets, and then run it thru investment type websites or run a website its self.  then after the serious mix.  It is then distributed to multiple users, then to the final transaction Traceable maybe, but it would take a very long time to figure out exactly who, and what it was used for.  think of a spider web with a grass seed stuck in it.