Stupid question and a stupid argument. Buying /selling drugs is illegal, so is buying /selling fake docs etc so why would anyone expect FBI to let such a service operate? Especially when sales numbers reach $1+ Billion and when the owner gives Forbes interviews saying FBI can't catch him? Let's get back to basics: FBI is supposed to enforce the laws. They do have some leeway in prioritizing, but a $1.2 Billion market…
The main difference in my eyes is that the DoJ is ultimately not worried about Colorado or Washington doing something "crazy" and legalizing all drugs, because they're part of the U.S. and ultimately dependent on the federal government. Silk Road was independent and sizable, and thus a threat.