I agree with you. I’m not stating that they are the creators of the marketplace. I should have been clearer about this .
Again, we are in agreement. But! … Human beings just naturally form marketplaces whenever and wherever conditions allow it. We can’t help ourselves. We as a species just seem to be wired that way. For example, Ebay! The trading of in game assets for real world $$?!! I didn’t see that coming! When I found out that that marketplace existed I was surprised and simultaneously not surprised because it’s simply another manifestation of the human impulse to form marketplaces wherever and whenever the conditions allow.
Now here is where I kinda disagree. Please note the text in bold because those words affect the applicability of #1 and #2. Points 1 & 2 are valid and astute observations not of the trading feature but of the marketplace itself because in ALL marketplaces where humans are involved fraud is a central problem. For example, let’s say hammers and nails enable people to make furniture (i.e., the mailbox system in this analogy). There is nothing stopping someone for selling a table as oak at oak prices when in reality it’s pine.