I can see your making a common mistake.
Just because someone's AIM, Email or whatever it says is "Insert moderator name here" doesn't mean they ARE them. Take notice of this because it's been happening somewhat alot now. You should confirm it beforehand because moderators/SMods are usually on mIRC or
GamerZPlanet Chat or via PM(although this method isn't instant) and it decreases your chances of being scammed.
EDIT: Also, be careful and pay close attention to the msn of the trader, sometimes there might be something off like l replaced with I, etc.