One story is about my friend who traveled to a jade trading shop and was surprised to encounter someone from his hometown. This person spoke the same dialect and knew a lot about familiar things from his hometown. As they talked like old friends, the selling agent started to sell him expensive jade. My friend was alerted, so he asked one trick question about the hometown and thus identified that the old friend was fake. He worked away immediately from the deceiving plot.
It turned out that every customer entering that shop will meet someone from their hometown. The owner has many trained agents who know every place. They asked someone in the shop to check your identity and then send the corresponding agent to chat with you.
Again, the influencing principle is liking: we tend to like someone similar.