I have proposed a trading format a couple of times that's used on Numista. I can search individual trade lists, see in an instant everything that person has that I do not, reference my trade list to his/her list of haves/don't haves, and select everything I want with a checkbox. The person reviews the list of what I want, what I have, and what they need. They come back with a list from my trade list and either agree to or disagree to each item I had selected off of their list. AFTER the trade is done you can rate the member from 1-5 stars on how good or bad they were. This is a coin site. I've done oodles of trades from France, England, India, Italy, Germany, Australia... etc etc you get the point. it's flawless and it helps weed out scammers. But the admin has never gotten back to me on whether or not they feel the idea plausible or positive.
The difference between Hoarding and Collecting is Structure.
~Kris~