I wonder if Silk Road is not much greater an innovation than we can imagine a first glance. I mean, if drug dealers are unknown, even for their clients, then they are probably unknown from one another. As a consequence, they can not use violence to impose themselves on the market. So in a way, Silk road style drug traffic could eradicate violence in the drug business, which would be tremendously good in my humble opinion.
"Eradicate violence in drug business" might be too much to expect, but if this business model grows, it can be tremendously good, yes.
The producers of drug themselves can sell the drugs directly. There's less need for a complex traffic network, carrying drugs all around the world from producers to consumers, frequently in different continents. This could considerably decrease violence, as you note. Not to mention the increase in customer's choice, quality of the product (gets you more high and/or less harmful to your health) etc.
I love what SR is doing, even though I've never bought anything there.
The main hurdle I see in this all are the mail carriers. If such business models grows enough, law enforcement will inspect with much more care every package that goes by. Some people propose anonymous mail carriers, maybe one day they'll exist...