This is the first thing that pops into my head because it was one of the first examples I was exposed to. When I was a child in NYC some guys would do these card shuffle games to part you of your money. The dumb people would play thinking they could win and the street smart ones knew it was a scam. I have no idea about the common sense thing, I guess I have too much of it and sometimes it can come across as being a know it all. Guess it's what I'm doing right now 