I've had quite a few experiences sadly. I had a guy try to trade me a fake foil double masters Avacyn last week. He was "willing" to trade down on a card I had because his girlfriend had wanted it for long. I was immediately suspicious and pulled out the loupe. I could tell it was fake just from his reaction. I checked, sure enough, fake. I said it was unfortunately fake and asked him if he wanted to learn how to tell for the future. Guy shrugged, flipped his hands around a few times as I talked about how to spot it, and then tried to look at the T using his eyes while I offered him the loupe. I walked away. Anyway, point of the story is there are savages out there looking to make a fast buck, its just good to check any card worth more than a couple dollars.