It's actually particularly relevant because someone seem to be making a serious effort at one using, naturally, Bitcoin: Sanjuro's "Assassination Market" (see http://www.gwern.net/Silk%20Road#future-developments for details).

It's hard to tell if AM's a scam or not by the nature of assassination markets, which turns out to be an interesting observation, IMO - it never occurred to me, reading the original speculations, that assassination markets would be so much harder to bootstrap than drug markets like Silk Road.