[cowtools]

The Silk Road.

But in all seriousness, if you are a vendor then any purchase by a customer that is not associated with a legally accountable entity must be settled with finality, because you have no way of preventing charge-back fraud yourself.

In cryptocurrency marketplaces, the customers vet the vendors, not the other way around. This is because the vendors have a higher upfront investment in their business and reputation. The customers are not expected to maintain a reputation (for sake of their privacy) or an investment (outside of an multisig escrow) so any attempt to vet them is prone to sybil attack.

The process of vetting customers is usually assumed by some monopolistic intermediary like PayPal. These companies are able to vet customers by implementing a mass surveillance system.