Itrader can still be dangerous, due to the fact that if a user and 100's of his friends wer to give feedback with each other, they would have 100 itraders each. lol
Forum's itrader may not be reliable since it can be subjected to manipulation. But it can be one indication of credibility. Better not rely on it solely especially if you make a deal involving big amount.
With iTrader, you need to provide a link, if the link is invalid or the two parties trading have not done business directly from that thread, the iTrader becomes invalid.