Right now u can get trusted ... but nobody knows how, what is the system? It is something arbitrary...
many users have done 1000's of trades, are always friendly and honest and will never get this tag.
Why not let the users vote for themselves.
System:
Every time u do a trade (and send/recieve FG) you can give the other user a plus point (only with a trade and a max of 1/week for the same person so u won't give mass points to close friends)
When u reach 1000 points, u get a Trusted tag. If a trade goes wrong (u get scammed) a moderator can adjust the points of each user and so removing TT or resetting his points. Even restoring a fraction if he decides to repay his scams.
just a thought, it will never be implemented ofcourse...