From The Verge article (http://www.theverge.com/2015/1/15/7553591/silk-road-trial-ro...):
"One of Karpeles' companies had registered 'Silkroadmarket.org,' leading investigators to consider him as a suspect."
Silk Road launched in February 2011: that's the same month Karpeles (or his associate at Mutum Sigilum) registered the domain