A decentralized blockchain based market called Syscoin just went online yesterday. It's completely decentralized (in the same way bitcoin is) which means that anyone can put up a listing and no one (not even the devs) can take it down. It's also open source. This system works perfectly as a DNM and it would render centralized markets like Alphabay obsolete. There's already a listing for MDMA on it.
Here's the download link. Check it out for yourself:
https://medium.com/@BlockchainFoundry/blockmarket-desktop-v1-0-release-b09ae68d07fe
So this place is gonna be where all the pedophiles start selling there pics? I prefer a marketplace that is able to take down the weapons, poisons and child porn.