But the Mom and Pop shop can now be anonymous and the evil druglord will have a hard time finding them since they can't go torture the street dealers that peddle Mom&Popshop & Co drugs.
There is no certainty of anonymity, especially in Mexico, for two reasons.
First, drug cartels have very easily control of the IT infrastructures, and second, they now employ hackers exactly to keep the internet information under control.
They've killed several bloggers already, and you can be sure they thought they were anonymous.
The cartels can employ all the hackers and torture all the bloggers they want but it will still be very hard to find sellers on SilkRoad. You will need to break Tor, trace BitCoins, trace deliveries, or trick sellers. This takes national or even international resources (NSA, FBI, Interpol, etc.). And they will have to do this in the US and Europe not Mexico.
First, drug cartels have very easily control of the IT infrastructures, and second, they now employ hackers exactly to keep the internet information under control.
They've killed several bloggers already, and you can be sure they thought they were anonymous.