Here's an academic analysis of Silk Road. After crawling the site for a few months they came up with this: http://www.andrew.cmu.edu/user/nicolasc/publications/TR-CMU-... "Abstract We perform a comprehensive measurement analysis of Silk Road, an anonymous, international online marketplace that operates as a Tor hidden service and uses Bitcoin as its exchange currency. We gather and analyze data over eight months betw…
Still, it seems like the risk far outweighs the gain here.