It's not simply that he allegedly built and maintained Silk Road — a secret Internet site on which criminals traded drugs and assassinations — for years.

And it's not just that he built a fortune in Bitcoins for doing so. The FBI alleges he earned $20,000 in Bitcoin commissions from sales on Silk Road per day, and made $3.4 million in total. "By far the largest balance held by any Silk Road user at the time," as the FBI wrote in its indictment.

Before he allegedly built Silk Road, Ulbricht was an engineer, studying solar cells as a grad student at Pennsylvania State University.