I would like to propose a minimum trade amount for items in the game that would automatically only allow that a trade take place if at least a 70% amount of the price has been paid by either player ,that way you avoid the effort it takes to look into people who don't do this and so that there isn't a "debate" on the matter in main chat taking away precious time from the game. You could then play the game without seemingly nice people getting you in trouble by giving you free items.

In summary it would lessen work for you in that you won't be looking for "criminals" and it would give a certainty about what can and can not be done in trading.