I can't say I know every detail of the case but I don't recall anyone getting killed or even hurt by Mr. Ulbricht so in my mind the punishment does not fit the crime. IMHO the death penalty should be off the table completely (go Nebraska!) and life in prison reserved for only violent offenders. You can argue that he enabled people to harm themselves but I think that's stretching it. If people want to take drugs, even take too much drugs their going to get it somewhere. If drugs were legal and treatment of abuse the focus instead of punishment Silk Road wouldn't have existed in the first place.
Instead of imprisoning for drug usage - provide treatment and rehab. It's cheaper and has better results. One could argue culture differences in drug usage, but that looks like an attempt to "knock it before you try it".
That's without going into how broken the US prison system is! See: privately owned prisons that require a quota to be filled [0].
[0] http://www.inthepublicinterest.org/article/criminal-how-lock...
Even if you're against the war on drugs I don't think you should really take it as a personal slight when someone operating on this scale gets arrested. Unless you really 100% believe that distribution of heavy narcotics doesn't damage society.