It's pretty simple. Don't trade with new members unless you're feeling lucky.
yeah... but some people:
a) Are naïve
b) Don't read
c) Don't realize that a scam can be a scam (i.e. the ticket looks legit but then the airline cancels it after 3 days etc.)
d) Are stupid
I realize that class d) won't get helped from some added precautions, but a), b) and c) might.
Even just a line under a new member's pm saying [Warning - This Member is new. Do business with them at your own risk] may help...