I'd also argue he almost certainly saved a huge number of lives with Silk Road: the ability to view eBay style feedback and chemical test results makes buying illegal drugs far safer than buying them on the street. On Silk Road people could buy from a reputable seller with a long history of providing unadulterated products, and could view testimonials from other buyers who had sent the products for chemical analysis.
I'm not surprised or upset at all that he went to prison, but unless I'm missing a ton of details (and I probably am), 12 years is plenty for what he did.