This is actually the most prime example of an 'untrusted' relationship. If it weren't for the total imbalance of power you have to bring the full force of the government down on a drug dealer without any need for a reason, you wouldn't do business with them at all.
If, on the other hand, you had to do business with the head of one of these multinational drug syndicates, you would start to understand this power dynamic more completely, as the power balance would flip. All of a sudden, the person you are dealing with no longer fears law enforcement. They are no longer a peon - they have bought off people in the government, acquired arms, trained a small army of their own, and now have to power to kill you or your associates without fear of reprisal. Would you still describe doing business with these people as a 'trusted' transaction? Of course not. You would start showing up to all your business dealings with your own goons, weapons, and armored vehicles. There would be zero trust that each transaction wouldn't end in a firefight.
Compare this to walking into your local bank branch, where with the correct documentation a typical local branch manager can give you a loan for over $1M without having ever done business with you before. That is the definition of a trusted transaction.
You've just become so desensitized to the marvel of it all that you might not be aware of what the alternative looks like.
How does a buyer do that on the darknet? Hell, how does the buyer do that on dealer that's part of a well set up network? Do you think cops don't know who many of the dealers are already? They can't or won't touch them, and as a buyer you have zero power to make that happen.
I don't know how's the market where you are, but I can assure you that nobody I know who buys or bought drugs ever even considered going to the cops - even when they got robbed and smacked around by a dealer.
If you were considering selling your company to Jamie Dimon - well, you can probably trust that he's not going to kill you, but you will show up with an army of lawyers and investment bankers to make sure you get a fair deal.
Example: open source is the communist model, and it works very well. To each according to their need, from each according to their ability. No one owns anything, and you're free to fork or vote with your feet.
Ditto for illegal drug markets. If you're unhappy as a merchant, you have a number of options. No one owns you. You can switch to a different market, or start your own (if you're suicidally ambitious).
The interesting part is that the drug markets end up combining the best of both capitalism and communism in that sense.
But only in that sense. Obviously, unregulated drugs are risky. Yet even without regulations, it's remarkable how rare it is to hear about unhappy customers.
Not sure what the right word is, but textbook-definition communism fits - open-source code isn't really owned in practical sense.
Open source is inherently communistic because nobody owns anything. You have control over your own project, but that's where it stops. You cannot force open source maintainers to do something. This is unlike capitalism; at a standard company, your NDA forces you not to disclose secrets. In open source, there are no secrets to disclose, short of drama and private infighting. A non-compete prevents you from forking the business you work for. These are unenforceable in Cali, but the rest of the US is not so lucky.
You are bound to a paycheck that determines your fate. This is the essence of capitalism.
Contrast that with open source: people don't merely contribute because they want to. It increases their reputation. Ditto for a review system on darknet markets.
Both of these things are very unlike capitalism. So if not communism, then what? Not libertarianism. There's no ownership, and ownership is central to libertarian ideals.
I think the question as a whole doesn't really make sense, since "open source" can't be separated from the whole economies in which it is created.
(¹ communists would object that the choice is often illusory or even non-existent, but that's another issue)
Yet we insist on conflating them, and argue against the one whenever the other is mentioned, as if it's synonymous with both.
The problems with the 'voluntary' nature of capitalism are best summed up by Anatole France: How noble the law, in its majestic equality, that both the rich and poor are equally prohibited from peeing in the streets, sleeping under bridges, and stealing bread!
EDIT: Point being, the economic milieu one finds one's self in, is that in which one tends to be obligated to participate — especially at the lower levels of power within that model.
That is: regular folk are trapped in the system they're born into. It is not meaningful to call their participation voluntary on their part. They may have nominally more freedom within the model in capitalism, but they're, on the whole, just as obligated to participate; they are just as much grist for the mill, under either model.
It's not even that their actions are immoral, it's that their judgement is so poor that you cannot depend on them behaving in their own long-term interest.
Maybe online dealers are different, but I would always worry it's just the same idiots behind a new anonymous account.