I don't know if this has been suggested before, but I think having a vouch trade thread section would be beneficial. I've seen it implemented in such threads as www.sourceop.com. Users are able to create reputation threads and have others post when a successful or unsuccessful trade has been done.
Example of a rep thread:
http://www.sourceop.com/modules.php?name=Forums&file=viewtopic&t=21652Benefits:
• Additional method (other than the 2/3 rule here) to assure user is a reputable trader.
• Good indication for games in which middlemen are hardly/never available for.
• (optional) - Could be an easier way for administrators and such to use this to promote highly reputable users as "TRUSTED" traders for certain games.
What do you think? Voice your opinion here and vote, thanks.