Thanks for the information, but are you not concerned with the barrier to entry this places on new sellers? It seems to me there might be quite a few people offering sporadic services and goods that do not warrant the investment a marketplace thread represents, and do not require the legitimacy it brings.
Could you tell me your considerations in regards to an unlicensed marketplace? A 'not endorsed by MMO, use at your own risk' type deal?
It could still potentially bring some value without the need for moderation, and could serve as a stepping stone for people building smaller services.