If a grocery store harms you in an illegal way you they can be punished by the force of the state in a variety of ways. The same is not true of a anonymous person on an inbound tor site.
If someone sold bad shit on the silk road, they'd lose all of their rep and stop making money.
On the original silk road, it cost a very large amount to get a vendor account. So if you decided to start selling bad shit, you'd have to play nice for a while to break even, a while longer to build trust, and then go out in a blaze of bad shit.
I don't really see why anyone would do that. If you have good enough connections to get a good rep on the Silk Road (or similar site), you have good enough connections to never need to sell bad shit. As Stringer Bell would say, it's all about the product. If you have better product than your competition, you'll win in the end.
Not the grocery store, the guy at some factory somewhere that peas into the soup that eventually makes it way to your shelf.
Point is there is a huge web of people everybody trusts to not be evil. They are trusted for no good reason (other than as stated most people aren't sociopaths). But some are. Protecting against them isn't worth the tiny risk of exposure.
Likewise fretting over being "defrauded" by anonymous (but reputed) persons whom you buy illicit goods from is not worth worrying about. Same with ebay, kickstarter etc.
> Do you ever buy anything at grocery store, drug store, restaurant that you put in your body?
These are all inspected by governments. You can argue that this is imperfect, does not happen frequently enough, leaves something to be desired, won't catch everything, etc., but speaking personally, I do take those inspection scores seriously when I see them posted on the walls of places.
It would not be controversial to state that the Federalist Papers were published anonymously, despite the fact that the authors gave themselves the pseudonym "Publius".
There is risk in everything. Generally people aren't sociopaths and aren't out to harm others. Risk is minimal but exists.
Sellers on Silkroad do have reputation? Anonymous does not mean "unknown".