I have another suggestion.
Maybe we could have a section/thread on Market forum where people could post their experience regarding trades with other individuals. For example: Tot the Grey, I had a good experience with this guy, everything went smoothly, he answers his messages promptly, everything went as we agreed. Or: I agreed with this guy to sell me +3 Claymore for 900k, then when we agreed he sold it to someone else, or: I waited for this guy to come back home from work, as he promised he will buy italian sword for 1000k, it's been three days and he never got back to me.
Or: THIS GUY IS A SCAMMER; HE RIPPED ME OFF!