The term Troll is used here for people who steal, lie, cheat people in the Sale/Trade forum.
A Nef is a loser who post stupid posts to get to "Golden Member" in like two days.
Take the Anandtech user Hardware for instance. He post anti-3dfx material every minute it seems like, with no proof, to get his count up. Just do a search for his name, and you see a Nef in action.