To what purpose? You have to go back to the real world at some point, whether buying/selling Bitcoins, or ordering something from your drug dealer. The authorities are more likely to get you at that point than at any other.
You don't exactly have to go back to the real world. What if you just wanted to run a site that would fall into a gray area legally or that you know would take a lot of fire from people. You could use tor and a webhost that accepted bitcoins.