If it could be tied into the DMV/Post Office/National ID card that would be the best. As it is there are a number of retailers that implement something similar;

If it could be tied into the DMV/Post Office/National ID card that would be the best. As it is there are a number of retailers that implement something similar; Costco for instance has a memberID card that has a lowrez photo on the back. Joining an existing ID system to a PKCS used with the website would be relatively straightforward. Your point about it reducing the universe of available buyers is true up to a point the variable there is the value of the goods being traded. Confirmed trustworthy identities aren't important if you're selling relatively low value goods, but if you're buying and selling cars, houses or industrial goods it suddenly becomes much more attractive to reduce the pool of buyers to those to on whom some due diligence has already been performed. As always; risk carries a premium. The basic problem of course is that our current monetary system is not well suited to todays internet.