My cousin was selling a piece of furniture on a website. People came to the house with cash. She got out her "pen". She told them their money was no good, the bank evidently gave them bad money. They left and she never saw them again but had gotten photos of their tag. Couple days later they were arrested. Funny money, stolen vehicle, bad tags. She turned the information she had over to the authorities which only strengthened their case. We usually donate to the curb.