Well a simple forum can substitute for a reliable feedback system, even if the lack of a startup fee allows more scammers to take a crack at it.
But this is what I don't see working:
Drug dealers would probably have to use an approach: "First taste is always free". Once client was confident with a very cheap or free sample of the product, the drug dealer could send products to the same client, that they would now have the address from, in any quantity desired, for the actual price.
Escrow is important. Without it it's way too easy to send someone the most killer shit they ever had in their life, then when they're baited go all tony76. It just won't work.
Also, I don't buy drugs online anymore by the way, but when I did I would have never bought from somebody who didn't need to ask me my address every single time. So sketchy.