It honestly hasn't when I think about it. Got the idea from this article:
http://www.panture.com/black-market-fully-utilized-bitcoin/ Basically, the drug business is HUGE. And that's only a part of the black market, (albeit a large part) imagine if drug cartels realized the benefits to using bitcoin. Nobody could steal their money if they secured their private keys well, nobody could rob em. If they disperse the earnings, it would be hard to trace em too. Once they start recognizing bitcoin for what it can do, an 8B market cap will be nothing in terms of whats to come.
If I was a local drug dealer, I'd accept bitcoin if I were given the chance. If law enforcement caught me, I could tear up any paper wallets I had on me. Once someone gives you the bitcoins, they can't turn around and try to scam you either. Opportunities for this are endless.