ATM the only (please correct me) marketplace that seems trully SAFE is The Marketplace. They use multi signature transactions, so all bad they could do is not release escrow and blackmail us - they can't steal anything. Vendor, customer, and admins have to agree for funds to be transferred.
Seriously, is there anything even remotly comparable?
Also, onion sites are compromised - did you all forget for how long FBI monitored SR servers?! Within i2p on the other hand each user is a node.