If there is a "be careful" check box option, it seems to me that there would still be the potential of Dave or Trish having to referee at some point.
Also, would the fact that a trade was agreed upon even be verified? In the past, I received a tree-mail requesting that I send a particular plant to someone who had just signed up despite this warning in the database:
Please don't ask the member for plants unless they specifically say the plants are available.
I chose not to respond. Would they now have the ability to leave me poor feedback (or a "be careful of") ?
Dave, if you do go ahead with a rating system, could a member choose to opt out?