I think there are some people who don't participate in the pond forum, and "new" people who only participate in trades, who are not to be trusted (yet). I've had a lot of experience with "trade only" folks who send lousy starts, or nothing at all. I've also had experiences with trade-only people that have been wonderful. All of the people here have been great, but I did get stiffed from people at the old Water Gardening Magazine forum. Anyone remember "Snowbird"?
There are some trade-only peeps, who don't really participate in the chat aspect, that have been great trade partners (like Magoo). So who's to say? It's the internet in reality... live and learn. Mail fraud is real (and prosecutable), though. If you feel you were jipped, there is alway the 'mail fraud' approach...
OTOH, I almost want you to name names. The feedback system here allows anyone to give any kind of feedback, regardless of whether a transaction actually occurred or not.