How would the exchange of goods happen? Could I just put up something like this up for auction, take the money and never ship (what I don't have)?
This doesn't prevent all fraud but it seems to work pretty well for dark markets.
Presumably any potential buyer has access to the ability to make your life very short and painful...
As far as I can tell, the only thing potentially binding darknet sellers is reputation, i.e. they want to be able to make further sales under this name. Even then, people run scams on eBay where they build up a sterling record selling small items for months, then "sell" something worth six figures and vanish with the money.
http://www.mirror.co.uk/money/ebay-buyer-seller-scams-fraud-...
I am curious why you thought this claim needed a reference. It seems like a pretty basic form of fraud everyone should be aware of.