In an editorial published last week in the journal, Addiction, researchers from the University of New South Wales, Australia, sought to quantify the movement of illicit online drug retailers to alternative marketplaces on the so-called "dark web". On October 3, 2013, the FBI shut down the Silk Road, the largest of these marketplaces for illicit substances, and often referred to in mainstream media as the eBay of illegal drugs. Since then, consumers and sellers have simply moved to other sites, which themselves have seen an explosion in the number active retailers since October 3rd.
Two sites in particular have seen dramatic increases: "Black Market Reloaded" has experienced a two-fold increase in active retailers, and "Sheep Marketplace" a five-fold increase. A new version of the Silk Road, "Silk Road 2.0", opened in November and had 92 vendors by their second day of operation.
Here's the graph from the editorial: